I liked both versions of University, but I preferred that of TS2. A few comparisons:
As someone who lived in a dorm for three years, dorm life in TS2 was more realistic (except we didn't have a private cook from midnight to 4am), especially in terms of the bedrooms themselves and the amenities. I found TS3's spacious rooms with the full-size beds to be a bit more unrealistic, as well as dorms that came with full gyms inside them.
I didn't mind having to wait an hour or two in TS2 for my Sims to go to class. At first I loved the idea of attending class with them in TS3, but it just became a headache, as there was invariably a huge crowd of people blocking the entry, and it usually took half the class period for my Sim to find her seat. And usually, she was quite uncomfortable because there was always some vampire stalking her amidst said crowd.
And while TS3 is more realistic with the ability to begin school at any age, I found it was too difficult to create a brand new Sim, get them enough money to go to school, and actually send them there. And it was super annoying having to send them back if you wanted them to get a degree. Again, more realistic, but I just didn't find it to be very necessary. I liked being able to get everything accomplished in one fell swoop in TS2, and being able to create a new Sim at said school without having to worry about being able to afford tuition.
The graduation ceremony in TS3 always took forever. I always wanted to skip it, but the game never let me. It was maddening.
I also liked that TS2 had more options for majors with more possible career paths.
The one thing I preferred in TS3's University? Backpacks.
