The only concern I have is that when resizing an image using jQuery, the browser would be resizing the image rather than something like Photoshop (or Flash). When a browser resizes an image it will generally look much worse than if you use Photoshop to resize it. If you prepare an animated GIF, all resizing will be handled by Photoshop (or whatever tool you use) and so will probably look considerably better.
Flash does use vector graphics, but that is only really relevant if you are going to allow the user to resize the animation - it will mean that flash is able to redraw it without losing quality.
I think in this instance, the animated GIF will be the most appropriate and accessible solution.