Hi! I have a Studio Cutter and love it! An advantage it has over the others is that it will cut up to 8 layers of fabric at a time. If you have lots of squares to cut, that is an advantage.
As far as the type of 5" die you purchase, I think it depends on how you will be using it. The more pieces you can cut at once will be less wasteful in the long run. I don't have a pinked die, so I don't know it that would be any advantage over the others. I don't really think I would prefer it over the others - would much rather have a "plain" edge. But, that's just me.
Also, there is a forum for those who use Accuquilt dies, however, mostly I see posts from people who have the smaller version.
Hope this helps!