There were some issues with this battle that really lowered my impressions of it:
-Paul was completely watered down, and there's no hiding it. 4 of his pokemon failed to earn a single win, whereas last time only one of Paul's pokemon was defeated without a victory. I can't accept that it's because Ash got stronger, because...
-Ash proved that he hasn't improved as a trainer. Um, bringing out Torterra against Drapion when Torterra has no strong moves against it? Failing to utilize Torterra's defenses and committing suicide with rock climb again? Letting his entire team (besides Pikachu) get badly poisoned? Then there's activating Electivire's motor drive again, forgetting his gym match that was 10 episodes ago (by the way, this basically negates Pika's win over Volkner's Electivire - I would have much rather seen Frosslass use destiny bond before being hit by volt tackle). Ash relied on Infernape, whose power honestly seems out of Ash's league (yes, there's Charizard, but Ash didn't train it for the most part and we had the obedience dilemma).
-Again with the Paul watered down bit, he didn't use many super strategies. Gastrodon's counter shield and domination of Staraptor was cool, and Drapion's toxic spikes and Electivire's pure power were cool. But Frosslass was too weak to pull off its strategy (no idea why Paul would choose it for this match) and Ninjask didn't even use baton pass. It was just a frail little fly that fell to one move that's supposed to be super weak against it.
-Infernape taking out half of Paul's team. This happened in Ash vs. Gary, where Charizard defeated Scizor, Golem, and Blastoise. But besides Scizor, both remaining pokemon were huge powerhouses (with Blastoise being his strongest) that had significant advantages over Charizard. This just made Charizard look even better. Infernape tearing Aggron and Ninjask apart made those 2 pokemon look weak (Infernape probably could have handled Frosslass as well, and hit Drapion with a flamethrower if Ash wanted). It just felt cheaper, and the majority of the battle didn't make me think "wow, Ash is a strong trainer."
Yes, Infernape vs. Electivire was amazing (and I'm glad this Electivire didn't use ice punch or iron tail like Volkner's), but I didn't really enjoy how the battle reached that point. I would have liked to see:
-A Buizel vs. Torterra rematch instead of Pika/Infernape vs. Aggron (remember, this was the very first match-up in Lake Acuity). Paul thinks he has a huge advantage, but Buizel uses its speed and powerful ice punch (or even an ice aqua jet based on its own ice power) to significantly weaken (or knock out) the thing. If it doesn't knock it out, Infernape could have done it with flare blitz (which would have said a lot more than defeating Paul's relatively weak Aggron).
-I'm not trying to advocate seeing Paul's full Lake Acuity team. Even some of his new pokemon could have been utilized much better, which a lot of people were expecting based on posts here. Frosslass using destiny bond on Pikachu would have been a good strategy that we haven't seen since Katie against Glalie (plus it would have spared Pikachu the humiliation of going down to Electivire after just beating one for the first time). Ninjask using baton pass to actually boost Paul's other players (such as making Gastrodon speedier or boosting Drapion's attack power to obscene levels, justifying pin missile's huge impact on a recovered Torterra). I wouldn't even have minded if Ash's Torterra still didn't get a win, but it would have been nice to see Ash finally understanding how to use it in battle.
For that matter, Ash vs. Katie is one of my favorite 6-on-6 matches (along with the first Ash/Paul match). Katie was Ash's first opponent to really utilize strategic switching. She knocked out Pikachu early and sacrificed her Misdreavus with a strategy that brought down Glalie. In the second half of the battle, Ash's Hoenn trio all battled well and got some wins. Corphish and Swellow fought hard, then Katie's Walrein nearly defeated half of Ash's team, but Ash actually battled smartly by utilizing Grovyle and the field to his advantage. The only downsides were seeing another Scizor and Torkoal/Pikachu being fall guys (but both got other wins during the league - Katie making quick work of them just made me think more of her as a trainer). No, this battle wasn't as epic (as Katie wasn't even a rival), but it wasn't supposed to be. For a filler trainer, I thought this was amazing.