I've always rendered animation at 720x480 frame size, usually called SD.  As I've mentioned, I'm always in "48 Hour Film Contest" mode, (a 5 minute animation in 2 days), where "time is of the essence".  And however they project the videos at the theater showings, the 720x480 looks pretty good.  The producer just adds black bars to fill up the frame, I think - she knows what I'm doing ahead of time.  I'm reading that "HD" is either 1280x720 or 1920x1080, so I'm curious what frame size you Carrara animators are using.  My video editor can handle all this, but I'm still leery of render times.