It's all personal preference really, you just need to experiment and find what works for you. In the last 12 months (since moving to 5s exclusively), I've gone lighter and ended up on .040"-.125" (previously Rotos, but now back on D'addario Prosteels). I was on a mission to make my basses as easy to play as possible, and combined with a low action and a lighter touch, I now find my basses so much easier to play. My hands feel much quicker and less inhibited getting around, is generally much more comfortable and easier to play.
If it's any help, I did a little poll last year to find out what other 5 string players use: http://basschat.co.uk/topic/179671-5-string-players-what-gauge-strings-do-you-use/page__mode__show