Both have Bluetooth, so I'm not sure what blkberryboy means.
The 7100 has speakerphone (7290 does not) and better ringtone playback The 7290 is limited to single track MIDI pretty much.
The 7100 also has a slightly better screen. Even though the Houston Real Time Traffic Map
would render at a smaller size on the 7100 than the 7290, it was definitely sharper on the 7100.
I don't think the 7100 has the two-level backlighting that the 7290 does, but I'm not sure on this one.
I ended up choosing the 7290 as I really didn't like the SureType keyboard on the 7100 (I SMS, PIN, and email a lot). I don't recall the 7100 really being a better phone reception and performance-wise.