>What am I supposed to do? Spend a few hours to try each one and find the best for my 13 years old i5 with a Nvidia gt440 that's used 3 hours per month?

The performance difference will be minimal. It's an aesthetic choice, pick the one you like the look of or give a few of them a try.

It's like cars. Some people have extreme opinions on matters, some would be fine picking almost any car, and most test drive a few before picking their favorite.

Yeah, I think the answer if you aren't sure which car to get is "any of the popular ones are probably fine for you" and that's probably true for Linux distributions and software choices too.