The n95 has a lot faster chip than the n73, plus a lot more memory, I am surprised you feel it slow. Are you running much other stuff in the n95 memory, when you are running GPS software? Trying switching the phone of, and then on again, and see if it runs any faster.
I used to have an n73 and it ran tomtom fine. only issue is that as the new maps come out they are not backwards compatibel and you need to move to a new phone for the new version of symbian to support the new version of tomtom to support the new maps. crazy.......