Mark IV by a landslide.
The triaxis is a jack of all trades and master of none.
While some would say the same about the Mark IV, I disagree. The lead channel is STELLAR for everything from Santana type leads to all out metal, the R2 channel can do just about anything in the rock spectrum and if you boost it it can do an awsome 80's thrash thing. The clean channel is among the best on any high gainer I have ever played.
The Triaxis is a good piece of gear, but I think it is way overpriced for what it is.
But, hey... if you find YOUR tone in it, that is really all that matters! :la: