Loop 2. Definitely 2
I think two is the best of the bunch by far. Much better than the other 4.
Number 1 has that weird buzzing thing that gets really annoying. I'd like it if the buzz were cut out.
3,4 and 5 all have these high pitched sounds that would get on my nerves over time. It sounds ok at first, but with the amount of time that I spend on that portal screen, I know it would get to me.
2 was interesting and funky, but subtle enough.