320x240 has an aspect ratio of 4/3, while 425x350 has an aspect ratio of 17/14. If anyone knows any standards for YouTube, let me know. In the hypothetical situation that there are just two of them (e.g. 425x350 px and 320x240 px), I guess and could work.

Hmm, I haven't been able to use PHP in BBCODE. WETWIIIRED!

"Stephen Wolfram is the creator of Mathematica and is widely regarded as the most important innovator in scientific and technical computing today." - Stephen Wolfram