Not entirely true. For me slapping is much better on a 4 and I'd probably go to a 4 with music from an era when that was all there was just to be authentic.
But quite frankly having played a 4 for MANY years I never was happy from the very beginning at the problem with horn keys (Eb) and jumping around the neck and the fact that I began music on piano and wondered why a piano had those notes but some how an instrument that was supposed to be "bass" didn't! Only back then I didn't have any idea what the solution was.
Then I got a 5 string and got used to the neck in pretty short order. But I tell you true, I really did not "get" what a 5 string is all about until I bought a 6 string. The 6er forces your game. No ball bat grips. MUST deal with and get comfy with a wide neck. and finally get down and learn those cross-neck patterns and how they can move up and down and side to side. And then suddenly the rain stopped. The sun came out. Birds were tweeting and life was good!
From that point on a 5er to me was just a 6er with the upper range a bit limited. When you aren't using the upper range you don't even notice the difference! So would I go back to a 4? Well I never really wanted to be there in the first place! But I've got a (doubled) 8 string which is basically a 4 and I play it. I play 4s now mostly when I end up playing someone else's bass. I've got a couple still but they essentially get zero play time. Changing keys and moveable patterns are just too convenient for my lazy butt to give up.
So yeah, there is a LOT of resistance to going back, It's not like I never do it, but I do need some relatively strong musical justification to give in to it.
