I have made a model in 3ds max, and I want to animate it, should I make that animation in 3ds max or in med?

easier and better in MED (my opinion)

in maya!

if you can animate in max, use max. (if it's a character, i recommend using skin modifier instead of physique, cuz FBX exporter of 3dsmax doesnt completely support physqiwue modifier.)

MAX or MED is the same animation you create, but in MED you don't need to export or import, just create and use