Optimizing battery life

If I were to back up one of my Blu-rays so that I could play it on my iPad using Infuse, would it make any difference to the power consumption of the iPad to encode the file using a format that the iPad can natively play? Since straight rips of Blu-ray movies are so large (fine for my media center, but not fine for an iPad), I’m going to have to convert many of them anyway… just wondering if I should use an mp4 container & AAC audio with the video optimized for the iPad (i.e. playable via iTunes), or an MKV & AC3 audio with the video optimized for the iPad (i.e. same as the first scenario)?

As long as the video is h.264 (which it likely is already) then the video will be played using HW decoding which provides for substantially better battery life.

MKV and AC3 audio should be just fine.