The Asus GL551 for sure. Better choice for a few reasons
http/www.newegg.com/Product/Product.aspx?Item=N82E16834232122
Has 16 GB of RAM vs most models of the Y50 which only has 8 GB. While you can get 16 GB RAM models price jumps to $1300+ on Newegg.com and Lenovo.com doesn't even list a 16 GB model atm.
Also I like ASUS laptops mostly for a) quality b) design c) cooling.
EDIT: Oops nevermind prices are the same, I accidentally got redirected to the canadian site. So prices should be the same. Though my reasoning still stands for picking ASUS.