One of the biggest concerns to me is file size. This forum has a limit on attachment file size, and that limit applies to images as well.
I don't remember what the limit is, but I ran into it with one animated GIF I was working on. IIRC, the Animated Gif was created by SnagIt, but it might have been ScreenFlow.
So, as I said, file size should be taken into account when considering options.