One thing to consider is how many squares there are per die. One of the advantages of a Studio over the Go! is that you can purchase larger dies that cut more at a time, plus you can cut more layers at a time with the Studio. I have a Go!, which is fine. One of the things I like about it is that it is easy to fold up and put away, taking up very little space when I don't need it. If I ever have both (1) enough money and (2) enough dedicated space available, I will seriously consider getting a Studio. I will look at the Sizzix also, but I'm not sure I want to be dealing with shims (necessary if you want to use Go! dies in the Sizzix). From what I have read, both the Studio and Sizzix are easy to crank. My Go! was stiff at first, but has gotten easier to crank with use.
Personally, I would not buy a die cutter just for cutting 2.5" squares since I enjoy using the June Tailor Shape Cut mat for cutting strips, and strips can be subcut with the mat into squares. There are some Youtube videos that demonstrate how to do this.
Unlike many, I do not enjoy using my Go! for cutting strips, squares, or rectangles. What I find it most useful for is odd shapes -- tumblers, squares (nips off all the dog ears which makes lining up with squares and other triangles very easy), circles, etc.