AT&T has been adding a little dash (and asterisk) of 4G to all its phones as of late, but not all of those handsets are created equal -- the Motorola Atrix 4G, HTC Inspire 4G and HP Veer 4G are technically capable of only HSDPA Category 10, which equates to maximum download speeds of 14.4Mbps. Not so for the new Samsung Infuse 4G, as it's been boosted to HSDPA Category 14, which bumps its particular flavor of 4G up to 21Mbps. That has AT&T playing in the same arena as T-Mobile, assuming that your local cell towers have the fiber backhaul in place... and assuming that T-Mobile doesn't make good on promises to deliver some 42Mbps (HSPA+ Category 20) handsets before AT&T catches up. And yes, the uploads should be fine, too -- AT&T says the Infuse 4G supports HSUPA Category 6, which should give us maximum rates of 5.76Mbps when firing files into the clouds.

The Engadget Podcast, live at 5:00PM ET!