I've played a Warwick 6 string thumb quite a bit. Didn't like it at all after the mystic wore off. the neck was so heavy you really had to hold it up to play it. The 4 strings may not be anything like that...Don't know. I do know I MUCH prefer my 5 string Cirrus to any bass I've ever played. Just kinda stumbled into the deal, too.
I still have a soft spot for a fender jazz 5, but I really don't need it.
My wife doesn't think I need so many, but you gotta be into somethin'. (I have 5 saxophones, too)