What is the best format for Video Podcasts?

I'm currently working on producing a video podcast, and I was just wondering what the most compatible format would be.

I'll be creating it using Final Cut Pro, using footage captured from an Elgato Game Capture HD at a 480p resolution - I'm not sure whether it's best to use a 640 x 480 resolution with a 4:3 aspect ratio or 853 x 480 with a 16:9 aspect ratio.