A very biased opinion:
A linear rail should give you a nice, smooth, straight and accurate movement. It is an engineering solution.
A V-groove system ... is not an engineering solution.
OK, I know, there are lots of V-groove machines out there. But they just don't have the accuracy of a linear rail.
On the other hand, if what you want is an inexpensive router for woodworking as a hobby, a V-groove might do. It all depends.
Cheers
Roger