Noob DX9 vs DX11 question

[sav]

I've not got the best setup - playing on a laptop, as my desktop only has Intel graphics - but to my surprise, the game actually runs. Which is great, even if the graphics are all turned way down.

I do have a question - what is the difference between DX9 and DX10/11? Both run on my computer, and if I'm not concerned about flashy graphics - can't really afford to be - which should I run?

Will DX11 run things faster cause it's newer, or DX9 because it's simpler?

I really have no idea... I guess there are a lot of non-power gamers out there wondering the same thing.