What is the MAXIMUM amp draw of your ESC and/or your motor(s) ? Take that number and add 10% (or more to allow for surges). Many switches have ratings for volts and amps.

Another option is to wire in a PLUG IN TYPE AUTOMOTIVE FUSE HOLDER and use a plug in fuse (lighter and cheaper). As long as your total amps are under 30 amps you should have no problem finding a plug in fuse.

The setup I have in a Freedom 3D is a CC 80 amp ESC with a Mega 22/20/2 motor. The motor draws a max of 46 amps the way I have it propped. To use a switch (or fuse) to kill the power to the ESC, I would need something for 50+ amps.

I have not been able to find auto plugin type fuses rated that high and the switches I have found that go that high are large and heavy (over 1 1/2 oz). That is why I use a switch to kill the power to the receiver and throttle. I had a glitch in the past that ran the motor at about 1/2 throttle for 5 or 6 seconds - scared the h*ll out of me. A 16" prop suddenly starting and running as you reach down to pick up the plane tends to do that