God bless field test.
I realized that when I turn on 3G I "automatic" have about a -20 dBm lose. It's not a Orange problems because I tried it in 3 or 4 locations and always having a -20 dbm worse result than GSM, while a Nokia 5800 in UMTS mode had full signal in all of those locations (my brother's phone, with orange too), no matter if I'm 2 meters away from the antenna or 200 underground
Why? I don't know, the only thing I know is when I called apple they offered me a exchange very quickly.