If you can swing the $$ then sod is the way to go. I've done both. Sod will give you the beautiful lawn from day one. Seed will take a good 2-3 years to fully establish itself. The watering will drive you nuts. Put in a sprinkler system using commercial sprayers which throw the water 50 feet. Take a look at the landscaping of banks, etc. They are gorgeous and are all sod with sprinklers.

Other:

Sod does not grow well in the shade, plant fescue seed in the shade. Surface prep is important and sod comes with a bit dirt on it already. Getting your clay-type soil ready for seed will be a pain.

If you do go the seed route, it will work given time but do not let the seed dry out (it won't recover). I used white large row covers instead of hay with alot of success to keep the birds away and moisture in.

Good Luck