Here's a good article on wireless broadband speeds. Note that they're talking about the speed you get using a modem card / air card, and not a smartphone.
Also, "Sprint 4G" and "Clear" and "Clearwire" are all one in the same. They are different sales channels for the same network built by Clearwire (in whom Sprint is a majority owner). Sprint's "3G" service is wholly on the Sprint network.
"The No. 3 wireless carrier, Sprint, claims to have a 4G network in place based on a different technology called WiMAX, though WiMAX is actually just an enhanced 3G technology..."