Well, I think they're the same thread. One of the sellers on Amazon is fabric.com, though, and the other is Peak Designs fulfilled by Amazon. So, they're not the same vendor.
I also think they're both the same size regular spool, not a cone. Both mention 1300 meters.
I've never been lucky enough to catch a fabric.com sale on Aurifil before they run out of the neutral colors I want. By the time I get to the sale, all the colors have an in-stock quantity of 0!
I have ordered in the past from this website:
http://www.sewezdesigns.com/Aurifil1.html and been very pleased. It's a little more of a hassle because her website can be confusing to navigate, plus she has to price-adjust the shipping. You do have to be careful that you are ordering the 50wt; I got confused on one order and got some 40wt that is now sitting in my drawer. I haven't checked her prices lately, but they were among the best when I ordered some time ago.