We've got a 4 banger.  Had the 7230 standard for about 6 months before trading that lemon back in on the 7130 premium.  Didn't notice much difference in power, I would say the 6 cylinder would probably hold on longer under load though.  Seems like if it gets in a hard pull you can't hardly drop gears fast enough at times for it to come back.  I never did figure out why Deere went from a 6 to a 4 on the 7130's though.