I don't know about distance but I've seen (and so has Jack and others) the AM units get squirly after awhile and would definatly give up some distance for accuracy. I usually don't see people driving their R/Cs to far away from their starting point.

The cost of $50 for a AM reciever is if you get a Kit version which would have to be the better AM recievers, otherwise for RTR it just comes with the car,but you can probably get an FM reciever AND controller for $50 on EBay brand new if you wanted to which works fine if your not looking to get to many R/Cs. Other wise its $70+ for a synthisized reciever every time you buy a car. Thats when it gets expensive if your looking to own alot of different R/Cs. I don't plan on owning to many cars/trucks but I'm probably gonna go with the JR controller anyhow just so its more convienent.