I'm actually finding that the upload/dl speed on myiPhone is slower than my Droid, using the 3G network. However, if i am on Wifi the speed increases dramatically. I ran a few tests using the 'Speedtest' App, and here are my results. I ran the test 3 times each. On the 3G network, and then using wifi:
3G
1st Test: Ping: 353ms/Download Speed: 0.12 Mbps/Upload Speed: 0.18 Mbps
2nd Test: Ping: 389ms/Download Speed: 0.15 Mbps/Upload Speed: 0.12 Mbps
3rd Test: Ping: 428 ms/Download Speed: 0.09 Mbps/Upload Speed: 0.07 Mbps
WiFi
1st Test: Ping: 84 ms/Download Speed: 1.31 Mbps/Upload Speed: 0.42 Mbps
2nd Test: Ping: 82 ms/Download Speed: 1.46 Mbps/Upload Speed: 0.52 Mbps
3rd Test: Ping: 78ms/Download Speed: 1.48 Mbps/Upload Speed: 0.54 Mbps
As you can see the results using WiFi are much faster. I'm sure my location at the moment has something to do with it (at work), however i am suprised at how much faster the phone Uploads/Downloads using WiFi. It's not a huge deal to me because i have WiFi access at both work and home, but it still suprised me a bit. The closest server that Speedtest could connect to was 22 miles away from me. I don't know how much of a difference that makes, but I'm assuming the closer you are the better.
Obviously your location, inside/outside buildings, etc will affect the results.
Hope this sheds some light.
*EDIT* I should of realized my office building was probably helping block some of the signal. My office is practically right in the middle of the building, away from walls or windows.