My high school has a video contest that incorporates projects created by students in SD and HD formats.
We will be playing these videos, along with graphic titles created in After Effects CS6 through Keynote as we have found this is ideal for our "award" presentation style.
I will be playing the keynote off my 2012 MacBook Pro 13" through a vga connection to the projector. We have a 600 seat auditorium, and our projector screen is quite large and definitely is SD (sorry i cannot provide more information regarding the projector).
We would like to have the highest quality video taking up as much as the screen as possible, so pretty much what i need to know is what would be the best format for our video? SD or HD. We'd be fine with letterboxing, just trying to get some help.
as you already pointed out, your Beamer is SD, so no need for HD files, specially not when the data runs through a VGA Cable.
It is more important, to use the right software to scale the HD videos you get into proper SD Files.
Also, I am not so sure if Power Point is the right software you wanna run this from, regarding image quality.