Gaming Laptop vs. Desktop PC + Tablet

A friend of mine is convinced that paying a custom PC manufacturer 2000 euros or 2561 USD to build a Laptop with the following specs :

(Display - 15,6" (39,62 cm) Full HD LED Display, NVIDIA GeForce® GTX 680M, Intel® Core™ i7 - 3740QM / 2,70GHz, 16 GB DDR3-RAM clocked at 1600 MHz and a hybrid 750 GB Harddrive)

is better than thinking about building a PC and getting a tablet for mobile use with that budget. I think he is being a total fool for doing that, though recognizing 2500 USD aren't too bad of a price to pay for such a laptop.He is 15 years old and his dad works in IT. Meaning support for good gaming (don't forget the display and keyboard) Could you suggest alternatives that blow this PC to pieces whilst leaving a big enough gap for a tablet ? I really need your support on this. Thanks guys.

desktops offer alot more customizability at a lower price.

$2500 is a shitload to spend on a laptop, or, to a lesser extent, a desktop. especially a 15.6"

laptops aren't really useful until college.... and I usually leave mine at my desk, in my room anyways..... planning on building a desktop for anything i need.....

a really good idea, one i thought about for a while, is to have a really nice desktop, and then get a laptop to use as a thin client....

$1200 laptop $1000 desktop  $300 tablet