When I saw him with UK this year, his bass sound (playing either a black Victory or a white Zon) wasn't really much different. With Asia, his bass sound is a little more subdued, but still pretty crisp. In the mid-sventies, he was very much perceived as a musican's musician bassist, Bill Bruford once said that at the time Wetton's bass playing was seen as the benchmark of cool.
It's ironic that in those days of his career, Wetton always felt that the singer/songwriter in him was eclipsed in his perception by other musicians by his bass playing about which, he says, he never gave much thought because it came largely intuitive to him. He was not a great rehearser at all.