Whatever makes you feel comfortable. What would the outcome be then? In your mind? I like that idea. So far, the outcome is pretty much the same as before.
Erase the Pegasi and they lose all weather control and the much faster flight travel (which would affect delivery and travel significantly). Unicorns could still operate flying machines and such but without weather control it would become unreliable as those air machines probably can't handle rough weather. Erase the Unicorns and they lose their main defense against evil forces. also a lot of knowledge would probably be lost too. some vital machinery may require magic to operate properly. Erase the Earth Ponies and they will lose a lot of man/horse power and physical labor. even if the other races could take over the Ponies job, the food production would probably go to standstill for a while and could probably cause a time of starvation. take away any of the three and and there will be great negative effects regardless of choice. I don't think I could ever make such a choice.
Y U NO pay attention! Unicorns used to raise the sun and moon before Celestia and Luna arrived. It's Canon!
Well, then that puts the Pegasi and Earth Ponies on even ground, in my opinion; the only advantage to keeping to Pegasi over the Earth Ponies is that it might be easier for Unicorns to learn to farm than to learn to govern the weather by magic.