This isn't something I've recently discovered, but I've never thought about discussing it until now...I guess I've got too much time on my hands (???) - Don't tell my boss!
Anyway, I've noticed when I play my 4-string, I tend to play more pizzicato and more horizontally on the neck, whereas when I play my 6-string, I tend to play more fluid bass lines, more in-the-groove and laid back, and more vertically.
Similarly, even from 4-string to 4-string or from 6-string to 6-string, I've noticed my style varies, depending on the feel of the bass and the general tones the bass produces.
Has anyone else noticed this in their playing?