The VT is going to be more versatile in the tones that it can drum up. The character knob with the drive knob will help you dial in a large range of tones from wooly to raging, but it does take over your tone and makes your amp sound like a VT Bass. That could be good or bad for you. The SFT is more interesting dynamically and colors your tone a little less, IMO. It has a more organic gain structure if you're looking to get a natural type of drive response. The VT sounds a bit more "modern" to me in its approach, whereas the SFT makes me think of a "vintage" era tube amp response. As mentioned above, the SFT has a few different versions and they are voiced slightly different. Same with the VT. Version one was without the amp sim and is sometimes regarded to be slightly "clankier".