HP Pavilion -15 ak007-tx V/s Asus GL552JX

Long story but HP's walk on the warranty has me always responding to questions about HP with a solid no. Read http://www.cnet.com/forums/discussions/which-laptop-is-the-best/ for the longer reply.

Can't trust them.

My son has the "ASUS ROG GL552VW-DH71 15-Inch Gaming Laptop, Discrete GPU GeForce GTX 960M 2GB VRAM, 16GB DDR4, 1TB (ROG Metallic)" and is very pleased. We did however swap in a 500GB SSD later.

that's a bit weird to do the comparison between the two. for gaming laptops, I usually think about ASUS, Alienware, MSI, and probably Lenovo. if your budget is limited to $700, you'd probably get these, or increase your budget to get a more professional one.
https://www.amazon.com/s/ref=sr_nr_p_36_2?fst=as%3Aoff&rh=n%3A172282%2Cn%3A541966%2Cn%3A13896617011%2Cn%3A565108%2Cn%3A13896615011%2Ck%3Alaptop%2Cp_n_intended_use_browse-bin%3A9647497011%2Cp_36%3A2421888011&keywords=laptop&ie=UTF8&qid=1468608629&rnid=2421885011

I will go for ASUS GL552JX between two options you’ve mention, however you can take this into your consideration as well. Here is the link. https://www.amazon.com/MSI-GP60-Leopard-Pro-825-15-6-Inch/dp/B00TI6TAJ4/ref=sr_1_2?s=electronics&ie=UTF8&qid=1469222970&sr=1-2&keywords=MSI+GP

An HP Star Wars Edition Pavilion laptop (as a spare). While mine isn't a gaming machine at all, the complete outside casing they put the guts in is the exact same one as the Pavilion you are considering. I must say that I am not overly impressed with the build quality at all. Lots of give to the display lid, bad trackpad, and fragile feeling ac adapter jack, which to me feels like it could break every time I plug it in. I know nothing about the ASUS you are considering, but I'm betting the build quality would be better.