I have used both the Olfa and Friskars and couple months ago decided to try the Gingher (bought them on eBay) for pennies on the dollar.
Both my 8 year old GD and I are left handed so I bought some left handed ones along with bunch of blades that go with them.
I prefer the Gingher. It is a better constructed cutter compared to the others. As the saying goes you get what you pay for.
I picked up a right handed one has well since I use both right hand and left hand equally while GD uses only her left hand.