As said in the above post, a 17" laptop would be unwieldy to transport—not only because of the size, but bigger usually means heavier as well, and I doubt you want a heavy laptop. 15" laptops tend to strike a better balance between computing power and size/weight—and would also have better battery life.
Also, a lot of people don’t use Windows for Web development. It’s certainly possible to use Windows, and I use it myself actually, but you might find that more people use either macOS or Linux, and in your case, I’d recommend dual-booting with Linux.
And using Linux on that 15" laptop, even though it may have less RAM, will allow it to stretch further since Windows is a far bigger resource hog than Linux. So get the 15" laptop and put Linux on it (Ubuntu is popular and works well), that’s what I’d recommend.