Eden imho is usually full of the beered up leary San an boys,and tarty girls but that is mainly because of the nights they put on - foam parties, Tonic, etc that club 18-30 send all their punters too.
Retro is different though, since it first started it has had a big worker crowd and less of the san an boys and the atmosphere is good. Last year Hed Kandi ran the back room on Retro nights and this was always rammed and great fun.
I actually did Retro for my birthday night last year as all my mates from Northampton who were working on the island (a lot for Retro) took me there, we had a really good time, everyone was really friendly and every tune made you want to sing along,lol.
If its busy again this year it'll be great.