I actually prefer the darker one. In the first pic with the lighter rug, I noticed it connected to the ivory couch, but my eyes couldn't decide which to really notice... sort of like they were competing. Then in the next pic I immediately noticed the dark pillows on the ivory couch and all the other detail I missed in the first pic. The darker rug compliments instead of competes, and it allows all of your other detail to pop a bit more. So my vote is darker.
BTW - we just moved and had to buy a huge rug. Looked all over and finally bought from
www.esalerugs.com. Saved $500-1000 by shopping there! I was concerned it wasn't legit, but we got our rug in a timely manner and all has been well since. I've since told everyone I know who is rug shopping. Good luck!