They're completely different beasts, so it's hard to compare
I've never been a huge fan of the stressful time-management aspect of the DR games personally
Again why Off the Record is a better experience: It has a time limitless, sandboxy game mode, where you can roam the locations without a time limit and just wreak havoc.
As I already said 3 times in this thread, so I think I'll stop saying for now: Wait for the Xmas Sale and buy OTR instead. It was 10 bucks back in July and it will certainly be on sale coming xmas.
Edit: However, I don't think Dead Rising 2 doesn't have its qualities. It's a new protagonist with a new story. I just think 7,50 is not a value proposition when Off The Record is a more complete experience. I'd wait for a lower price point (which won't ever happen anytime soon, but hey).
I think playing both back-to-back would be too excruciating, so I personally rather play the more complete one (OTR) and MAYBE buy the other one for completion sake down the road.