Read some of the reviews here. Another package is Mapopolis, which, IMHO, is the best currently available for most users. Routis is also really nice, and PowerLOC Navigator is very competitive. It becomes a matter of style and your own pattern of usage that determines which might be "best" for you.
I have had an Ambicom 802.11b WiFi CF card for some time now, extreamly pleased with its ease of setup, performance and compleatness of drivers and overall operation.
Ambicom appears to have a very good track record with there products, I give them 2 thumbs up. Hope that helps anyone exploring there product line, included the above mentioned GPS card.