Probably sacrilege saying this on a Nagatoro Chapter comments section but I prefer Uzaki though not by too large of a margin. Both are fun series to read but I prefer the fact that in Uzaki it's two character personalities bouncing off one another. It's all in how Uzaki's extroverted and excitable nature drives her into trying to pick on the introverted but stubborn male mc but she's so bad at it that it either backfires or ends in her taking damage as well. Fanservice also there but used as a comedy point rather than in the traditional sense which makes it more tolerable but not by much. On the other hand, in Nagatoro-san it feels like she's the only major personality and senpai is there to accentuate her personality and not react to her. Nagatoro is front and center all the time and without her, no one else really has a chance to stand out. Senpai without Nagatoro is not a character. It makes him really hard to identify with or find some common ground with. At least for me. Personally, I find it easier to relate with the male mc of Uzaki-chan. Both are still great reads though please don't get me wrong
Basically it my mind it's:
> Uzaki chan is about two different characters and their struggles with dealing with one another's very different personalities. Fanservice also helps, I'll be honest.
> Nagatoro is about one character using another one as a reason to explore the first ones personality. Senpai has little to no real presence in the manga.
At least that's how I see it