Here are some of the more popular reasons I’ve encountered on why people prefer tables over benches:
1) It’s easier to learn on tables
2) It’s a move away from the big noisy bench-based shuls of the past
3) It’s a warmer and friendlier atmosphere when people sit on both sides
4) It’s a good place to keep your seforim and tallis bag
5) It’s easier to put on your tefillin
6) It feel like your davening in a Beis Medrash
7) It’s easier to get in and out of your seat
It should be noted that many people prefer Lavi seating over both benches and table.
Relatively straight-backed chairs are best for my back. Next best is a wooden pew. A table is helpful when the siddur/machzor/Chumash/… is heavy, and for putting on tefillin. I can do without theater seats in the round or otherwise.