That is, if you feel like installing your own SSD in the laptop. If you do, get a Samsung 850 EVO or Pro. There are subtle differences, and the Pro will last longer. But you'll pay a premium for that.
If you don't feel like installing your own SSD, you're stuck with what the manufacturer will put in it (and they probably won't tell you what brand it is).
I'd probably stick with an Intel CPU, preferably in the Core i5 or i7 range rather than i3 (or worse yet, Pentium or whatever their mid-low range is these days). No preferred type of memory, other than a large amount (8 or 16GB if you can swing it).
Screen type is a fairly personal choice, but my preference would be a high res "retina" type; e.g. 2650x1600 at 15" or better. I don't know how many of those are out there.
