Advice for WWAN upgrade on T500

[jgjg]

I've got a T500 (20553AU) and I'd like to enable wireless broadband. There are a lot of options to choose from, so I'm looking for advice to narrow down the list of choices.

For example:
- internal card or external USB modem - which do you prefer, and why?
- hardware preferences - once I make the internal/external choice, which WWAN modem model do you prefer, and why?
- provider - which WWAN providers have you had good experience with? (especially while travelling in major US cities including New York and San Francisco where I hear some networks have trouble)

I've Googled around alot but haven't found an objevtive, comprehensive guide for choosing a modem and provider for my ThinkPad. If you know of one, I'd love to know the link!

Thanks!
JG

P.S. - Apologies for such an open-ended question, as you can tell I'm early in my search.