Significant... for now... my point is that the difference is shrinking... used to be that gaming laptops were easily twice or even 3 times as heavy... now it's less than 40%.... in a few years, probably closer to 10%...
As for form factor, as bezels get decreased across the board, 14" and 15" gaming laptops will almost certainly arise that will be even smaller... Remember the Alienware 11"? I wonder if something similar will rise again...
Basically, we have always had to sacrifice performance for size/weight in the electronics industry... but as technology increases, these sacrifices become less and less... cell phones used to be bricks, now they're tiny... computers used to be the size of rooms... now they can be less than an inch thick... as this tech increases, the lines blur between portable and performance --> soon we'll have both in 1 package