re: Fortune favors the bold
Actually, there would not be that much difference in contamination levels, certainly not enough to make it worth the cost.
The mechanics of impact ejecta have been studied, and quite likely the pieces from Mars would fall back to Mars or head off into space, rather than accrete into the moons we see today. But that's one of things that makes the junk imaged by MRO so intersting...
We know from their spectrum that Phobos and Deimos are made up of different stuff than Mars...
Could Phobos and Deimos have originally coalesced near Mars? Aside from the difference in compositon, they also have spin: they're in orbit around Mars.