I don't get the "well all these other players use a 4-string so I'm in good company."
Feh - I'm not anyone else. That argument only holds water if you think about playing instead of actually doing it. When the downbeat hits the rest of the band and the audience don't care who's "company I'm in."
I can see why long time 4-string players stick there. 5-string is a different mindset and approach - *if* you actually incorporate the B into your playing. A lot of guys don't - they use it as a thumbrest and then whack some über low notes. If that works for you, fine. That doesn't really work for me.
I recently tried (again) to pick up a 4 after 11 years on nothing but 5-strings (was a 4-string player before that). I can "relearn" to play the 4, but then I am messed up on the 5. I know that many/most don't have this problem, but I do. The B-string is totally incorporated into my approach to the instrument. Due to a number of factors (both desired tone/attack and physical limitations), I don't spend a lot of time down at the nut. Because of the way I pluck, I want a fatter note. And due to tendonitis nipping at many joints, I don't want to be doing extended reaches to the nut a lot. With a bass with a great B-string (eg my Roscoes), I can play F on the 6th fret and get a great tone. And while staying in that position I have about 2 octaves range without having to shift position. I tend to favor a vertical approach to playing, especially if I'm sight-reading something.
That said I still like the simplicity of 4-strings, not having to worry about damping the B when playing up the neck or slapping/chording, and being forced to rethink my playing can be healthy. But for me once I get in a 4-mindset, when I grab a 5 I have to totally recalibrate. Ends up being too much thinking...that's the last thing I want to have to do. So I'm back to just 5 strings. Frankly the damping and slapping/chording can be addressed by technique so that is just time in the practice chair (or sofa).
Playing a 5 and staying a little up the neck also gives you a "short scale equivalent" bass and all of those benefits (ease of playing, etc). And you also have extended range on both ends (low and high) when you want it. I find it to be an ideal compromise for the music that I play and how my approach has evolved. But everyone has their own needs and has to find their own way. While looking at other people's experiences is valuable, I don't think that playing a particular instrument because some famous guy does really will end up getting you the most benefit for your playing needs unless you're just playing for fun in your house. In that case, play whatever makes you happy. But if you're gigging you have a responsibility to the band, the audience, and the music. So you need to figure out what works best *for you* and execute with it.
