Funny, I am also considering these two system types.
From what I've gathered, jpeyton and BTA are spot on, the Celeron's raw processing power is leagues above the E-350 and leaves you with a lot of headroom for other things later on. I've been reading about the E-350 vs G530, and while yes it is better with wattage it is only by a small margin, with the E-350 needing to stay at a higher % for longer periods vs the G530 barely working at all and sleeping most of the time.
A good friend of mine has an E-350 and with a wattage meter he see's 27w draw while playing an HD movie, other anecdotal accounts have the G530 systems using 30-40w playing similar quality files.
Personally I will be buying a similar system for my M350 today.