Paint works for some things, but the real measure of the program is how FAST you can make images. The longer it takes, the fewer frames you will end up making, and the choppier your animations will be.
That's one of the things that differs between commercial and freeware programs. Photoshop is set up to process multitudes of files.
For instance, when I want to convert a game to a smaller resolution....its nice to run a batch resize. 400 png's resized in about 1 minute.