I just put a DQ6 in a build... it's a great board!! Could be a bit of overkill for anyone not considering OC. It does come with some very nice bells and whistles, such as firewire and full Vista 64 support (only driver issue I had was an add-on wifi card), though I'm sure the DS3 would have Vista support too.
I loaded this into a Cooler Master Cosmos (nice case but BIG), and what I liked about it was that the mobo has headers for all 4 case fans. A great thing to allow you control fan speed through bios ro windows apps. I'm not sure how many fan headers the DS3 has, but I'm dl the manual now and will get back.
Can't go wrong with Gigabyte. I think the decision comes down more to features... if the DS# has everything you need, buy it. If you needs the extras on the DQ6, buy it. If you have money to burn, no contest, buy the better board - DQ6.