Advice for buying laptop

I'd say go with the dell, it has an SSD for its boot drive so it turns on faster, plus the GPU is the 4g variant.

The asus has a bigger screen and 16gb of memory, but you can upgrade memory in the dell with the money you saved.

Sources:
http/www.newegg.com/Product/Product.aspx?Item=N82E16834232770&nm_mc=KNC-GoogleAdwords-PC&cm_mmc=KNC-GoogleAdwords-PC-_-pla-_-Gaming+Laptops-_-N82E16834232770&gclid=CjwKEAiAw4e1BRDfi7vghaWU9jESJACzo9juWkd6bJ6R3gyyQ8IGaz8BAkAAWsC7hpWQqkTdjjFqpRoC3D7w_wcB&gclsrc=aw.ds
http/www.newegg.com/Product/Product.aspx?Item=N82E16834298771R&nm_mc=KNC-GoogleAdwords-PC&cm_mmc=KNC-GoogleAdwords-PC-_-pla-_-Gaming+Laptops-_-N82E16834298771R&gclid=CjwKEAiAw4e1BRDfi7vghaWU9jESJACzo9jucn211DEoenSnyPmY6rSfJc_mONO9RPTI7qAeKQytfBoCcDbw_wcB&gclsrc=aw.ds

Honestly I wouldn't bother with the SSD. Most games don't get much if any loading improvement from having an SSD so you'd only want it for the boot drive, which the Dell already has for you. Spend that money on getting more RAM if anything. If you do want to get the SSD though, check the form factor for the HDD in your laptop. (It'll probably be the 2.5 inch.)

I'd buy it off Newegg. It's cheaper than the dell price you quoted, and yes you will get the full dell warranty and everything in the box.
Think of Newegg as the tech focused version of Amazon.

It sounds like you want to have a lot of space to install your games, so look for a laptop with two hard drive caddies. I will say, the other person who posted that said you do not need an SSD is incorrect. I always recommend installing SSDs. You can get a 500GB 850 EVO (great choice, by the way) for $159.99 on Amazon as of the time I am posting this. When it comes to gaming, you really do not need more than 8GB of RAM to have your games play smoothly. You'd want to focus on getting a laptop with a good graphics card. Upgrading to an SSD from a regular HDD is a world of difference. We're talking read and write speeds of about 100-140 MB/s compared to 550 MB/s. Everything on your computer will run faster. Game loading screens will be much shorter and you can spend more time gaming. Let me know what other questions you have.

When installing an SSD, I recommend making it your boot drive so Windows and all of your applications run smoother, and then any games you install on the SSD will run smoother too. The problem is that with either laptop you will have to disassemble it and replace the HDD with an SSD, unless one of them happens to have two places to install hard drives. Most laptops only have one space for a hard drive, and these laptops look like they only have one as well. In either model, you can replace the 1TB HDD with your 500GB 850 EVO and it will fit perfectly. At that point, you could buy a hard drive enclosure off of Amazon like this (http/www.amazon.com/Inateck-External-Enclosure-Tool-free-FE2001/dp/B00DW374W4/ref=sr_1_3?ie=UTF8&qid=1453497142&sr=8-3&keywords=usb+3+enclosure+inateck) and put the 1TB HDD in and use it as an external drive. You probably wouldn't want to install games on the external drive, but you could keep your pictures and videos and documents on there to give you the most free space on your 500GB SSD. If you're not comfortable taking apart laptops or installing Windows on your own, you may be better off bringing it to a repair shop and having them do it professionally. It's not horribly difficult, but can be daunting if it would be your first time and there isn't much support information regarding disassembling either of those laptops as they are so new.

I see what you're getting at now. To the best of knowledge, there is a 1TB HDD that operates on SATA III and an 8GB SSD that operates on the M.2 interface. One Amazon review said that a single screw gets open an access panel that lets you see both of these drives, meaning replacing them would be very easy. If it is in fact an M.2 slot and there is enough room, you should be able to install the M.2 version of the 850 EVO. Link here:
http/www.amazon.com/Samsung-850-EVO-3-5-Inch-MZ-N5E500BW/dp/B00TGIW1XG/ref=sr_1_2?ie=UTF8&qid=1453499057&sr=8-2&keywords=M.2+Evo

However, that being said, I cannot confirm that the hard drives will be easy to access and I also cannot confirm that it is an M.2 slot for the 8GB SSD. That is my best guess. You might try calling Dell support and getting more information from them.

UPDATE: I found the service manual from Dell and can confirm that it is in fact an M.2 drive. Here is the complete service manual so you'll know exactly how to take it apart and replace the drive.

Service Manual: ftp/ftp.dell.com/Manuals/all-products/esuprt_laptop/esuprt_inspiron_laptop/inspiron-15-7559-laptop_Service%20Manual_en-us.pdf
Reference Guide: ftp/ftp.dell.com/Manuals/all-products/esuprt_laptop/esuprt_inspiron_laptop/inspiron-15-7559-laptop_Reference%20Guide_en-us.pdf

Please let me know what other help you need.

Great, glad I could be of assistance. You should be good to go to purchase that Dell laptop at this point and you will be able to replace the 8GB SSD with an M.2 500GB 850 EVO, as well as keeping the 1TB HDD installed. Please select my solution as the best answer if you think you have everything you need now. Happy to help on any more questions you may have.