its easier on system resources to render separate files out instead of an AVI which if for example is done in an HD format you would a end up with a monster file size at the end of rendering as maya does not compress. Its actually easier to render the images as the files will be smaller in size then its a case of getting them comped together.

Also advantage of rendering image sequences are you can stop the render at anytime for whatever reason and then have the choice to go back and continue from where you left off. Ideal if a frame needs fixing up. this is not an option with AVI, you'd have to start over.

JPGS are not ideal in these circumstances really unless its a desperate situation LOL

Either stepped keys are good or multiple cameras it doesnt matter, but if you dont want the hassle of editing then Gects method is the way to go there.

Jay