Fairly different beasts - the VT Bass is all about amp modelling, and as such has some inherent tonal characteristics that carry through the whole pedal. The Westwood is less so, being listed as a "translucent" drive, though with it's powerful EQ it can certainly cop something akin to a pushed SVT (though minus the speaker emulation the VT Bass can deliver).
The two would complement each other pretty well though - you could run the VT as an always on tone, and then really push it with the Westwood.
I'm using a westwood like this currently with a few other drive pedals (Darkglass VMT, Hamstead Odyssey), basically providing a slightly dirty boost, with the lows pushed to fatten things up, and just a touch of treble presence/sparkle. Works fantastically like this, though it also excels at drive verging on distortion all by itself.
It's worth noting it's not hugely dissimilar to the TC MojoMojo, though it's clearer and more open sounding in the top end, and the Bass frequency of the Westwood really seems to get particularly punchy when pushed.