To assume that you will be higher just because of the fact that you are commencing a climb at DH/MAP instead of at rotation on the rwy is like taking a wild guess of how your profile will look a couple of miles ahead and it is very foolish. Keep in mind that for a SID in mountainous terrain you can have an additional required climb gradient, f.e.x 8% till passing a certain point/altitude. You have to be certain that you will be able to achieve obstacle clearance in the missed approach path before making a decision like that. But I know most of you guys live in relatively flat areas and you don't need to take such factors into consideration, however applying such a rule-of-thumb in every situation is not recommendable.