Herd instinct - that's all. At the moment I think the DS3 is within £2 of the S3 anyway so why not get it.
The boards are identical apart from the DS3 using solid Japanese capacitors. Why solid capacitors? Well, about 3 years ago there was a Taiwanese capacitor factory that supplied all the big motherboard manufacturers and they had a quality problem that meant motherboards made with their capacitors tended to fail in very unpleasant ways. The few manufacturers that were building 'enthusiast' motherboards with Japanese capacitors didn't have the same problem and a myth grew up that Japanese capacitors were the answer to life, the universe and everything. In the US market having solid capacitors is a major selling point, so they made 2 versions of the 'budget' motherboard - the S3 which everyone in the far east buys because it's cheap and it clocks well and the DS3 which they can sell to Westerners who'll buy anything if the marketing is right. The S3 clocks just as well, but it will only last 3-4 years whereas the DS3 will last 6-7 years.