I actually read through both fights in the manga (and watched Part I in the anime) today, and now I have some updated impressions if you're interested. Just so you know, I will mostly be talking about the negatives I noticed of each fight when compared to the other one, as I've already gone into detail long enough about why I think both battles are my favorite of their respective portion of the series. With that understood, here you go-
Part I: First of all, let me start off by saying the fight in the anime was WAY better than in the manga. After reading it, I still thought it was a very good fight, but I didn't remember loving it like I used to. It just didn't seem as awesome as I remembered. And then I watched it in the anime, and I completely felt different- this makes me believe 100% that the anime can absolutely make a fight so much better. Besides that, I never noticed how much filler content was added in the anime. I'd say about 25% (maybe even more) of the anime battle was all filler content. However, that's not a negative, as a lot of that is responsible for making the fight so amazing in the anime. With that said, that makes me believe the anime will also make me really enjoy the Kaguya fight, which wasn't anything mind blowing in the manga, and will make Naruto and Sasuke's second battle even better than it was in the manga (but again, more on that later).
But getting back on track, this was still a very entertaining fight; one of the best in Part I. The length was perfect at 11 chapters (218-219; 225-233), and not too many panels were wasted. The best word to use for this fight would be "escalation", as it constantly builds by having them gain more power as the fight progresses. Its fun seeing them start out basic and then gaining more power as it continues. If anything, I would complain that we didn't get to see them battle at their most powerful forms, as they cut straight to the final clash instead of continuing the fight.
While there is a lot to praise in this fight (which I have done numerous times in the past, which is why I'm kind of skipping this part- if you want to know why I like it so much, ask me and I'll explain it then), there were also a few negatives that I wanted to bring up. First and foremost, I do think the reasoning behind the fight isn't really that plausible or that engaging. I understand why Naruto is trying to bring Sasuke back (in fact, I've gone through a similar situation, and so I can relate) and while it is admirable, I'm not sure it was handled in the best way possible. Often, it led to the dialogue being very repetitive and stale after hearing Naruto and Sasuke say the same thing over and over again. Speaking of the dialogue, I also noticed that there was a lot of talking in the fight; more than I previously thought so. While this is not necessarily a negative through and through, it slows down the pace of the fight and completely interrupts the momentum it had before. Talking is a necessity in a fight like this, but it is important to know when it should take place; in this fight, there was a moment in nearly every chapter where they would stop to talk, and as previously mentioned, it mostly just restated the same statement that was said in the previous chapter, adding nothing new to the argument.
Next, I would say that flashbacks also dragged down this fight to a certain extent. While there were times when it was beneficial to the story to add flashbacks, there were also times when it was completely unnecessary. The biggest problem would have to be the five or six chapter flashback of Sasuke's history, as it completely interrupted the entire momentum the battle established until then (please keep in mind that I actually really like this flashback; given the tragic nature of it and the fact that Sasuke is my favorite character, it probably one of my favorite flashbacks in the entire series. It just probably should not have taken place right in the middle of the fight).
Finally, I just want to point out that I actually noticed that not a lot happened in this fight (in the manga). While it was much longer than the battle in Part II, that battle actually had more happening than in this one. I think the problem often stemmed from most of the panels in this battle were focused on showing every little movement of the battle rather than speeding up the pace of the battle and allowing for more content to happen. Again, it's not a huge issue, but definitely something I noticed. And once more, the anime added so much more to the battle that this problem completely evaporated after watching it.
Part II: Before I start off with the criticisms, let me say that I think this fight will be 100 times better in the anime than in the manga. Almost every issue I have could be solved in the anime, if done right (which after talking to that source, I do believe will be the outcome). With that said, I will once again mostly be talking about the problems I had with this fight, as I've already made it clear why I believe it's one of the best fights in the entire series (if done right in the anime, could be my favorite). But before I get into that, let me talk about some of the positives when compared to Part I (basically, where I believe this fight shined where Part I did not).
First of all, it must be noted that this fight is extremely different than Part I's as this is no longer the same series- it has evolved. Many say they don't like how Naruto turned into a series capable of creating large chakra avatars and mega explosions, but I am not one of them- I loved all of the large techniques and explosions. I'm an action junkie, and it doesn't get any better than seeing things go boom. It's just a key difference- if you don't like that stuff, then you understandably wouldn't like this battle that much. Next, I also think the scenario in which they were fighting was much more interesting than Part I's was. While it was still primarily based on Naruto trying to save Sasuke, it also dealt with the fate of the world and Sasuke's goal of revolution. Ultimately, that just interested me way more than Naruto's simple mission of bringing Sasuke back to Konoha from Part I. And because this was way more engaging, it also made all of the dialogue in this battle much more interesting as well, as they had a lot more to say this time; in a sense, the dialogue was just much better than Part I. That, and there were also specific moments that were reserved talking instead of interrupting the battle at random moments to have a heart to heart; it just made the battle flow much more naturally. Finally, as noted before, a lot more happened in this battle than Part I. There were a lot more moments of exchanging attacks/techniques, and (in the story, not in real life), it also was much longer than Part I (that's mainly due to the two-page spread in 697). This was mostly due to Kishimoto adding much more content into the battle instead of showing every single little move that slowed down the pace, like in Part I. With the explanation of what Part II did better than Part I out of the way, let's get into the negative aspects.
Undoubtedly my largest issue with the battle was the length. In my mind, the battle went on for about 7 chapters, from 692-699 (allow me to explain- half of 692, half of 693, 694-698, and finally the first three pages of 699 where Naruto and Sasuke make the Seal of Reconciliation, effectively ending their conflict; if you want to know why I feel this way, ask and I will explain). I always believed this battle should have been at least 10 chapters, with 20 being the maximum amount (it probably shouldn't have been that long). With that said, despite my enjoyment, there is still a large amount of disappointment that I'll probably never get over. It left impression of it being rushed and somewhat lackluster after ten years of waiting. Despite the fact that a lot happened, it just felt way too short (of course this is a huge aspect the anime will improve; by the time it's animated, it most likely will be extended with filler content and won't feel so short).
Another aspect I was pretty disappointed about was how many little abilities Naruto and Sasuke used in this battle. Not only am I talking about the Sage abilities they acquired (Tailed Beast powers for Naruto and Rinnegan for Sasuke), but also the ones they had previously before meeting Hagoromo. For example, Naruto should have used more clones, Rasengan/Rasenshuriken variants, Sage Mode, etc, while Sasuke should have used more of his EMS powers (Blaze Release and base mode Susanoo), fire/lighting release techniques, Kirin, etc. Overall, there were so many techniques at their disposal and they didn't make use of them all. One could argue it's because they were so tired after fighting Kaguya, but they honestly didn't look that exhausted so I won't take that as an excuse. And even if that was the case, then Kishimoto should have waited for them to heal/regenerate chakra before having them fight. And yet again, this is another issue that will probably be solved in the anime, as many of these elements will most likely be added with filler.
The final major issue I had with this fight was, yet again, the use of flashbacks. Granted, there were certain times when the flashbacks were used very well- better than usual in this series. However, given the fact that the fight was cut short due to the five week deadline, these flashbacks should have been cut in order to add more content for the fight itself.