The UMC is good, cheap ammo. I have found it much cleaner burning and more reliable than the WWB, and a bit more potent than Federal American Eagle. UMC is also made in the USA; WWB is foreign. I have had several duds with WWB over the years, probably fewer than 1 in 1000, though. But I've never had a UMC dud.
I'm willing to pay the extra ~$1 or so per 100 rounds for the higher quality, US-made UMC ammo.