I wouldn't worry much about 4k miles. If the owner changed the oil even once and maybe cleaned the AC a couple times how bad could it be? When I worry is when a machine is dirty. I feel a dirty bike has an owner who doesn't care much about it.
What about the changes that have been made in the model between 07 & 09? Has Harley updated anything in those years to make the 09 a better bike? Therefore worth the extra cost.
....buy the '07 if you like it. You'll have several thousand dollars left over to buy parts so it's YOUR bike.
I bought my '06 1200R with 2100 miles, and took it on a 5,500-mile trip last summer... I am convinced it never got broken-in until it had about 6,500 miles on it... the motor got quieter, and I swear it's quicker... or I'm just older and more scared. I think it's still under 9,000 miles, but it runs like a top.