Hi
Have you had any thoughts on the 4 vs 5 string? I'm having the same problem myself. I've played using my fingers for years on a 4, then a 5 string. But recently I have been using a pick which I only seem to like doing on the 4 string. Problem is, I love my 5 string (Ibanez EDB555) but not my 4 string (battered old Tanglewood Rebel). I'd love to hear if you have made a decision and why you made it.
A possible solution is you have lighter gauge strings is to tune the 5 string to DEADG. I tried it on mine and it was OK but my strings are a really heavy gauge and the B string sounded a bit crappy. I'm not sure if this is a recommended solution by anyone else, but each to their own I think.