I just picked up a WIIO from Tone Factor (great on line store....no problems at all) It sure looks like it says WHO when you glance at it. I don't have a leads, but I can compare it to a VT Bass.
The WIIO is much more mid present and touch sensitive. The touch sensitivity lets it break up as you pluck harder and clean up when you back off. The VT Bass is much more Hi-Fi sounding and when you pluck harder the tone does not change that much but it gets louder and a little compressed. The distortion on the WIIO is less blatty than on the VT-Bass. I couldn't get the Entwistle sound out of it, but I'm playing a P-bass with flats.
I'm running the WIIO in the loop of a Radial Big Shot Mix. This lets me mix in some clean signal. I boost the highs and roll off the lows which gives me a big fat sound with Mid to high freq distortion that is very touch sensitive. On its own the WIIO will break up when you play louder. With this set up I can increase the volume and add that high end break up when I play harder. It also has a much more solid bass sound when I mix in the clean signal. I run this signal into the VT Bass, which fattens things up and gives me more compression and a sheen to the high end if I want it.
So now I have full on Ampeg sound (VT alone), Hiwatt with added bottom (WIIO in Loop) or both. I like it, but I have not had a chance to play it with a band yet. It does sound good when I play along with our tracks.