I'd just like to throw my 2 cents in here and say that IF you can, wait a bit. The new Nvidia and Radeon cards are currently being rolled out, so if the possibility is there, wait and see if they're going to announce any new mobile GPU options. The newest generation from nvidia offers until-now unsurpassed power management, meaning that you'll get more performance, with less heat. Also the new Pascal GPU is an absolute beast. (Pascal is 10XX cards, i.e GTX 1080).
Do NOT under any circumstances, whatever you're considering, buy a laptop with AMD CPU and/or Radeon GPU. AMD and Radeon are notorious for being extremely hot, and while they're built with higher heat-tolerance in mind, it still needs to be cooled properly, and with higher temperatures comes greater risk of something going wrong. Technically, from what I've heard, their performance is subpar compared to Intel and Nvidia, and since you're going for laptop, the amount of performance per watt of heat is critical.
For gaming on a laptop, get a proper cooling pad to put the laptop on. Even if this puts a strain on your hand for having to reach the keyboard, keeping the computer at least somewhat cool makes a huge difference; and a cooling pad with fans make that difference. (Get an external keyboard that you can use, I'd recommend this regardless. Laptop keyboards can be uncomfortable in the long run).
The two computers you linked are both all right, I've had no bad experience with Dell myself, but Asus ROG laptops are (from what I've heard) built to last. I have significant experience with Asus desktop hardware, it's pretty decent.
i7 vs. i5 is mostly a moot point, on a regular basis the i7 doesn't give all that much more performance in a game (maybe a few frames extra per second or something). One thing to consider though, is that the new Doom game recommends a high-end i7 desktop processor in their specifications, and while I choose to take such recommendations with a pinch of salt, it is going to become more of a trend for high-end games to utilize the available power that more powerful processors offer. I disagree with the statement made earlier in the thread about laptop i7 being comparable to desktop i5; unless stated in the specifications of the CPU, an i7 has 4 cores and hyperthreading (meaning 8 logical cores to work with, meaning the processor can do more stuff at the same time), while an i5 will never have hyperthreading. In the case of multitasking operations, i7 will always trump i5.
Sorry for the long post, hope I didn't completely overwhelm you. If you have any questions, just quote me here, or send a PM.