Hi folks. For what it's worth, I'm strictly 4-string too. I can see what is attractive about being able to get higher or lower notes, but in my opinion extra strings can encourage left-hand laziness, and wider necks are so unappealing to play.
If I was going to change from 4 strings, I'd actually go for fewer! Some early classical basses actually had three strings, tuned 7 semitones apart. This combination was supposedly a very versatile one. The Japanese company Atlansia offer a 2-string bass. Why don't some top players adopt the minimalist approach? I suppose most of them are too busy trying to sound like guitarists.