Those are two (well, three depending on how you read the title) top shelf power amps, possibly the highest regarded guitar power amps ever made. They all sound “big and transparent” basically. What you put in is exactly what you get out.
I don’t have much experience with VHT2150’s, but I have a VHT 2/90/2 which is described as being the closest you can get to a 2150 without actually being that amp.
My opinion of my VHT is that it’s a very loud, fast, exceptionally clean amp with minimal (if any) natural compression, and it amplifies the full bandwidth of anything you put through it, and it won’t break up unless you’re almost maxing out the Volume knob pushing volumes that to be honest there’s almost no reason to ever approach. It's about as close to a tube hifi system for guitar as you're going to get. I'd imagine the VHT2150 would sound similar to this.
However, the VHT does have a depth control where the Mesa doesn’t so I suppose you could say the VHT technically has more tone shaping options. But if you’re using an Axe-Fx you can already shape whatever frequencies you want so that’s really kind of negligible.
Both amps are super loud, super clean and transparent, super fast, and 99% of guitar players wouldn't ever take them anywhere near their limits so neither are likely to add any extra "tube compression" or anything like that to your sound.
Either one will be more than good.
