Garmin seems to be the best one to go for, but Tom Tom has come a long way as well. I have a friend that owns an older Garmin and he LOVES his. I don't know anyone that owns a Tom Tom GPS, but I have heard a lot of great things about them and how good they are as well. I would really be torn choosing between the two myself. For me though I would look into the features that YOU want and/or need in the GPS and then base your final decision on that. Both GPS's you listed have got some great reviews and I don't think you would go wrong with either one. Look up some reviews on each and then find out what features each has that you want to use or need and then go with your gut feeling because I don't think between the two you could go wrong.
My wife use to work for a place that sold GPS's and she has said they had a lot of happy customers with Tom Tom and as well and of course also with Garmin. My wife was actually the one that tuned me in on the Tom Tom being an excellent brand as well right up there with Garmin. I use to think of Tom Tom as some off brand, but not anymore.