I'm a great lover of GoDaddy's DDC. You get the lowest prices GoDaddy offer without having to worry about hunting down a discount coupon, which often doesn't work for Renewals or GoDaddy Auctions. Whereas your discount prices applies to everything, registrations, transfers, renewals, auctions. So just for the convenience factor I recommend it. But of course you need to figure out the savings and how many registrations you need to break-even. So it's really only good if you have about 200+ transactions a year, on a purely monetary level.
As for transfers. I think you can get a special price if you are transferring 25+ domains to NameCheap. But you'd need to ask them the terms of their bulk deal because I'm not familiar with it. They particularly like you to transfer domains from GoDaddy. So don't be shy in saying your transferring from GoDaddy.