That's precisely where I would think it would not matter. I don't have the equipment to do the experiment you suggest (as you might have guessed from my question), but I believe you.
Other threads had more or less convinced me that for my purposes, I did not HD and would have some downsides from that. I just don't see needing the HD... but it is tempting at current prices.
I think I'll look around for an SD cam that's not SD (i.e. Std Def that's not flash)!