I mean a 33 is a good score, but it's not very competitive for most top schools. Don't settle for a 33 if you're confident you can score a 36+ (confident being the key word here, don't retake a 33 unless it's quite a few points below your AAMC test average and you know you can do better). I agree that retaking a 33 to get a 34 or 35 is not a good use of time. And of course, it will look bad if your score goes down the second time.
OP, like others have noted, most schools will take both scores into consideration in some way or another.