I have a DX6i, but honestly don't use it that much. All of my tanks are set up control wise exactly the same, and I find I didn't really need to customize the set up for each tank. So I just use one radio.
Also I am a proponent of building a movable electronics tray, and moving the electronics around between tanks. I feel it make little sense to have $200 of electronics sitting in each and every tank. Ideally about 4 complete electronics setups will satisfy the needs of most. Typically when you have multiple tanks you will find that only a few at a time are on your "Hot list" the rest are shelf queens until your interest turns to them again. So why have all that money tied up in them sitting on the shelf.
That's where the Benedini shines. I was planning on doing the same, but I only have Tamiya now. I keep 4 Tx on hand so I can have a battle in the backyard. I switch the tops of the T-34 and SU-100 since the hull and engine are the same.
If I was running HLs, I'd absolutely just decide which tank I was to run for the day, load the appropriate sound file and be off to battle.