I think it's something of a tradeoff. I've messed with Streets&Trips, Mappoint, Mobile PC and iGuidance. The MS programs are the easiest to import address data into and to do multi-point routes with the data. They have tremendous flexibility in managing the data that I haven't seen in any of the others.
But Mobile PC has the best route guidance. Once you pass a "via" point (Mobile PC equivalent of a "stop") it is gone from the route and Mobile PC is quite lenient in determining that you have passed it.
I haven't done much routing with iGuidance. In particular, I've never tried multi-point routes in it. Perhaps I should do that one of these days when it's too ugly out to play golf.
...ken...