I think your best bet is to research the ones your interested in to see if you like them and if they have the memory capability you seek.
Depending on your brand preferences, price range, etc.
Best Buy says this about TomTom Start 50 which sounds intriguing:
"Up to 7 million points of interest guide you toward interesting and useful destinations." 7 million! Sounds very intriguing!
You can ask your Best Buy Salesperson for help in that matter, they are very knowledgeable about their products.