See I kinda like the challenge of playing things on a 4, I think i'm part of the Jeff Berlin school when it comes to that! Plus I feel that I can lay into them a bit more, easier to throw about to my mind.
Having said that, I definitly see the application of 5 strings, I've used them (and am probably going to buy one) just for dep gigs whereby the singer turns up 10mins before a gig and changes all the keys, i'm an alright player but transposing on the fly stresses me out lol.
So I think my conclusion is, 4 strings are where I'm at, they're on the same wave-length as me, I love playing 4's and I have more fun doing so. 5's are a tool to me, they are there to do a job.
I know that seems like an odd conclusion, and I can't really explain it, but hey, that's the human brain huh!
Si