blotunga: My only real advice would be that if you don't mind the extra size and weight, get a 17" screen. You get a numeric keypad and a lot better cooling. Plus 2 HDD/SSD slots at least.
At least the 15.6" Acer (Aspire E5-575G) I picked up has a full keyboard wih a numeric keypad. If I compare the keyboard to my 17.2" old ASUS ROG laptop, the main difference in the keyboards is that:
- there is a cap between the main keyboard and the numpad on the bigger ASUS, while on the Acer there is no such cap.
- the arrow keys are located in a bit more comfortable way on the ASUS and the up/down keys are bigger.
- the cap between individual keys seems to be a bit bigger on the ASUS.
The keys themselves are the same size etc. Also, 90% of the time I personally tend to use external keyboards with laptops anyway (either a normal USB keyboard, or a smaller wireless Logitech keyboard if I am on the road). I just like that ability to not have to be hunched over the laptop, if not necessary, and of course the external keyboards are usually more comfortable (no chiclet-keyboards).
I am unsure about this Acer laptop, but I've seen some other 15.6" laptops with two HDD bays (EDIT: According to
this review, it has two HDD bays). It might be related to modern laptops not having internal optical drives anymore necessary (this Acer doesn't have; but then it has an extra VGA out port, which really baffles me :D), so maybe now 15.6" laptops have enough room for two hard drives as well. And with this current SSD insanity, I guess everyone needs that bigger extra HDD anyway as those measly 256GB SSDs just don't cut it anymore. A couple of modern AAA games installed, and it is full. Thank you and goodbye. (I am thinking if I should take the SSD out of this Acer and put a 1TB or 2TB HDD inside instead, just so that it won't easily run out of hard drive space...).
To me, 15.6" laptop size seems to be optimal. It still feels small enough to want to carry in your backpack and even take out when you are on the road, but the screen is still big enough for comfortable use. My 17.2" ASUS doesn't fit into normal backpacks, and its charger is a size and weight of house brick.
It is probabaly true 17.2" laptops have better cooling options due to more room inside but I'd think that matters more if you are looking for the very highest end gaming laptops with the hottest-running new GPUs (like GTX 1080 or what is the highest end in mobile GPUs at the moment). It appears to me that when NVidia makes new iterations of their earlier high-end mobile GPUs, they also make them use less power/run cooler than their predecessors, so they don't necessarily need as much cooling.
I haven't run any demanding games on this Acer yet to see how cool it runs, but I intend to burn-test it a bit. I am still clean-installing Windows 10 on it to get rid of all the crapware Acer has preloaded in it.