they certainly are nice to have. i use it and i could notice a difference, which definitely says a lot in my case. still, they are not necessary, and if you can keep the string centered yourself then you don’t need it.
I really like my KK just because it throws very smooth. After the two or three day break in, it goes and goes. I have noticed that it snags sometimes, but it’s not really that bad. Just make sure your hits are precise.
IMO I think kk bearings last longer because I’ve had one dry for over a year and it still spins like the first day I got it.
C-tracs are the same concept but play almost identical.
So I would say get either a kk or a C-trac.