Yeah you need the MEP rating in both scenarios, so it cancels out. Wasn't always the case - I never held an MEP rating and that got a few heads scratching. I think they closed that loophole a few years ago. You need 6 hours for the MEP, 1.5--2 hours for the flight test, min of 2 for the MEIR conversion and 1.5-2 hours for the flight test. So you can get the MEIR with 11-12 MEP hours vs 23 hours the 'normal' way.
The true savings will be considerably more once you account for the extra hour building that you don't have to do.