Wouldn't blowing up 240p look more realistic though, like real security camera footage? One of the problems I had with Paranormal Activity 2 (2010), is that the the security camera footage looked way too HD and clean, and sounded too clean too. You don't want to have that lack of convincing, unless I wrong of course, or looking too hard.
In JFK (1991), they blew up the actual 8mm Zapruder film, and that looked and felt much more real, than recreating it at a higher film resolution. The movie never got any flack for the Zapruder films point of view looking terrible.