I have both and they are quite different. If I had to choose, I'd keep the Quilt Cut. I had it first and it made my cutting so much more accurate. I use it for everything, from cutting out shapes to squaring up blocks.
Now, the Accuquilt is great for cutting out shapes (assuming you have the proper die) but it doesn't help with trimming and squaring things up.
I think the Quilt Cut is more versatile.