Dogtra is the best and works. Tri tronics makes a great product too.
No one else has anything even close. i use the dogtra, because they work with my training metods. I have used a 202ncp for the last 3 years almost everyday from Sept. till May. they are a deal for 2 collars under 300.
I would strongly advise you to first learn the proper use of a collar. It is a training tool not a punishment device. Still most pro trainers don't know the difference. When used properly the collar to the dog is no different from a check cord or pinch collar.