Are you planning a walk-in style coop? If so, you'll be happy you built it bigger rather than smaller. Raking through the litter and checking that all is in order in the coop is much nicer when you're not constantly bumping up against the walls. We've got 10 Australorps in a 7'x8' coop and I would not want it to be any smaller. It's so nice to be in the coop with the chickens if I need to get close to them to check up on something. I also have the sense that the litter is going to be easier to manage in a larger coop. There are more dry shavings to mix in with the poopy ones - I'm doing the deep litter method without poop boards - and so far so good. My birds have been able to free range during the day since we got them, so they're only pooping up the coop at night. I also think a larger coop gives you more options for ventilation away from roosting birds. I know that smaller coops are better choices for some people, but the larger walk-in style is really the best fit for us.
You also mentioned being able to have the coop closer to the house. Our coop is about 150' from the house and I'm amazed at how convenient it is. I popped some broccoli into the microwave for 3 minutes and then went out to the coop to close all the windows and doors for the night. When I got back inside I still had 15 seconds to go on my veggies. Taking care of the chickens takes surprisingly little time.