You go-around at whichever comes first. If your ROD is slightly greater than needed, you'll be at MDA before the MAPt, so go around (as we don't do the level flight bit). Same deal if it's the other way round, and you reach the MAPt at some height above MDA.
This does all assume that you are not visual. Had to do one the other day, and came out at MDA showing 3 reds on the PAPIs i.e we were a mile or so short. But as we were then visual, we could continue level for a bit to get back on the profile. The three other a/c that followed us in all came out to MDA at a similar position, so it seems that it wasn't my cr@p flying that got us there!