I came across a great deal on a Purple Cow 2-in-1 12 inch cutter (it is rotary on one side with interchangeable blades, and guillotine on the other). It was too good of a deal to pass up, so I grabbed it without even researching it, and have been very happy with it for the last 3 years!
I think Joan B is right though... there are so many options, and it really comes down to personal preference.
The Crafty Sister
Designing for: YourNextStamp, C.C.Designs, WhimsieDoodles, LittleMissMuffet, PaperieInk