My 2 cents:
It's kinda like arguing about the best deer hunting rifle. You can kill a deer with just about any calibur but everyone has a opinion.
I started out with a box cutter, found they work pretty good for some things. I used a box cutter for a couple of years before I discovered the round knife/head knife.
What I can do with a round knife I can't do with a box cutter is:
1. cut curves of many different radius',
2. cut a straight line without a straight edge for a guide,
3. skive
4. I can see where I am going with the cut
I didn't think the learning curve was that great for me. The key is to get a good sharp one, buy one that comes sharp so you know what sharp really is. I know not everyone will agree with me and that's ok. Use the tool that works for you,
Happy cutting,
Doug