The main difference with Bitcoin Diamond is that they multiplied the supply by 10. If you had 1 BTC before block 495866, you now have 10 BCD. This is done by moving the decimal point rather than making the coin more divisible. That is, with Bitcoin, 100 million satoshi = 1 BTC. With Bitcoin Diamond, 10 million satoshi = 1 BCD. Its really just pure marketing.