Doing it full time, I like to try to work smarter, not harder...so whatever method it takes to do that is best.
I tend to use the vinyl cutter for lettering only. I think some designs I do with liquid mask would be impossible for me to do with a vinyl cut design.
Also, I think you are able to be a bit more liberal with the paint when using liquid mask. Over doing it with paint on vinyl I find is easier to create an uncrisp edge.
As said, the main thing is to work smarter not harder....so whatever is needed to acheive that is the route I will try to take.