There is a radio thread in the developement forum with all the files and instructions you need, follow them closely. You can flash whichever radio you want in that thread and I don't think there is a clear way to tell which is "best" unless you know someone in your area that has tested the different radios, it depends on your location, carrier, distance from tower, etc. Some give more siganl but drain battery faster, some are battery meisters but siganal is not so good. Try a few and see what works best for you, just remember to follow the instructions carefully.
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Device: SGN II I-317M
My evolution: Dext-->Desire Z-->Atrix 4G-->SGSIII-->SGNII
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