I much prefer D2D. I've never been a fan of anything that requires online activation. No offence meant here, but it's another example of an American company thinking that the whole world is like America... ie. always online with reliable internet. That is simply not the case for many people. I also travel around, and am often stuck in a hotel with no internet access etc. Steam does work most of the time but I still don't like the idea. Download from D2D, make your own backup, and take it on the road with you. Miles better.
It's also just the idea that you have to rely on someone else for something. In the old days you bought your game in a box and looked after it, and you didn't have to phone anyone or go online when you wanted to install it again. That's how it should be. Steam goes against my grain.