Depending on how sensitive your dog is, I would not use the Sport 50. I started out with one of those and just could not get the right level. Level 2 didn't even slow her down and level 3 was too much. So then I tried it on a level 2 continuous and it was a little hotter than level 2 nick. I could still not find just the right level for this dog. I don't know about the other collar you are asking about but I would not go with the Sport 50. They do have new Sport 80's I believe that give you a few more levels to work with, you may want to try one of those.
Good luck