These questions really speak to me.
Honestly? I prefer a little bit of both in all cases. This post definitely reminded me of things I wasn't extremely fond of in the transition to 3e and why I think 2.5 continues to be a valid choice if you're able to swallow and understand it all, though. There are certainly balance considerations to take into account either way that more or less even things out, but regardless.
Considering the character I transferred over from 2e to 3e, even though the concept remained the same, the changes to his overall backstory and presentation were pretty extensive to account for 3e's directional differences. I think it was for the better, though, as it brought the character more down to earth.
The character was supposed to be skilled at martial arts, social-fu, and sorcery, which stretched things thin and required careful adjudication of xp even in previous editions; in that regard, martial arts and sorcery essentially switched places. Sorcery was once the extensively gatekeeped area of expertise while martial arts was easy to jump into and grab charms from. In 3e, Sorcery has become easier to dip into, while martial arts is something that requires deep investment. In my opinion, neither 2e or 3e got this right - in both editions, both skill sets either have too many or too few hurdles. Mechanically speaking, though, things have worked out for me in both editions once I've gotten a handle on the system, so I can't complain too much.
>Do you prefer Ex2's 'sorcery is sorcery' or Ex3's 'sorcery is whatever it is'
I liked the trials because they were extremely flavorful, but in a meta sense they were a series of backstory checkmarks to justify being able to learn Sorcery. They did go a looong way towards demonstrating why not everyone could learn Sorcery, though.
>Do you prefer Ex2's Thaumaturgy or Ex3's 'only special people' Thaumaturgy
The former is better for the setting. 3e's fits the real-world definition better, though.