I had the 1080p IPS in my Alienware 17 R2 (as far as I know it hasn't changed) and I was happy with it. I would not get a 4K in 17" size as there is no available mobile video card that can come close to properly supporting such a resolution in games. I also would not opt for the 1440p because it is TN, I much prefer IPS. Although two benefits (at least according to specs) are that the TN is brighter and has GSync.
At most I'd possibly consider the 1440p screen, but I know if I was buying again right now, I'd get the base 1080p. It's a really good resolution for the 17" size... no scaling needed and looks very sharp. And, from personal experience, I thought the screen was quite good!