RE: what is the best RC transmiter out there?
The hotrodders used to have a saying: "speed costs, how fast can you spend?"
"best" is a pretty broad term. If you're into radio assisted Old Timers, an $800 high end 2.4 rig is an absolute waste of money. A cheap used DX5 or used functional 4-ch 72mhz gear will work fine.
If you're into $20K turbines, then maybe used trash gear isn't what you're looking for...