Both bands started out in the late 70's as innovators in post punk early synth songs. Both bands had hits, maybe OMD had marginally more, and then both bands fantastically crashed and burned by over producing everything and chasing the dollar. OMD marginally kill it again by having songs in two of John Hughes' teen angst films.
Whilst I can forgive OMD as they readily admit they fucked up, Simple Minds just carried on up their own arse.
Saying that, both are now fantastic in concert and play a hell of a lot of their early stuff. I still have shivers at what might have been with Simple Minds as their early stuff was amazing.