The I-4 will save money, be better for the environment and quite possible hold better resale as gas prices rise. It is also a lot of fun to hear that DOHC engine wind up, and with a 7.5 sec. 0-60 time (Car and Driver) the car is no slouch. The V6 does have a slightly tighter feel to the suspension due to the lower profile tires but I was not willing to give up 3-4 mpg for that, especially with gas headed for $5 gal in a couple of years.
I just picked up a new Royal Blue Accord EX-L with the I-4 here in Sacramento for $21,500, which is well under invoice. It was one of the last ones on the dealer lot and I consider it a killer value.