As someone who owns the XPS 15, I agree. The new XPS 15 is really great, and the battery life is incredible. My only complaint is the trackpad, which they have not totally fixed from previous models. In previous models it tended to get very mushy and somewhat unresponsive after about six months of solid use.
I too am going to college in the fall for engineering, and have been looking at similar choices, so I'll share what I've found with you. The first option I found was getting a Blade Stealth. It has an i7, long battery life, and is ultra portable. Along with that I have considered getting a Razer Core so that I could do things like game do 3D modeling with no problem whatsoever(the i7 will handle most 3D modeling applications with no problems at all). There are other options, like an XPS 15 with the 960m, which is a great laptop, although it runs a little hot. The P40 is a good laptop, but is pretty expensive for the hardware included.