Nightcrawler - I'm familiar with the M60E3. The Marine Corps used 'em until 93 or 94. It was a substantial improvement over the earlier models, but doesn't hold a candle to the M240G in my book. Like BigG says, teh 240 is bulletproof. A worn sear is one of the things that will cause a runaway gun. I can't tell you if the sears are more likely to wear on a 60 than on a M240G tho...
You can wear out the sear on any MG by squeezing/unsqueezing the trigger too slowly and firing bursts that are too short. Proper trigger operation on an MG is NOT like on a target rifle -- it is to move the trigger to the rear and fire a manly burst of 5-7 rounds, then release the trigger.