I think its more about what features does the radio have, instead of how many channels...........
I believe the R50 is limited to mechanical mixing but you should probably get a radio that supports CCPM for the future. Also, 5 band throttle/pitch curves are really nice! And don't forget remote gyro gain. I'm going to buy the JR 8103 soon. I think its a radio I won't outgrow for awhile.