Consider:
-Samsung's is VA and the other IPS panel (for VA better darks, poor-er viewing angle)
-Samsung's display is curved
There's likely more in differences that i'm missing.
If you want to use it in a room that has low light levels, samsung's is better, you wont get as much of the backlight greying out your black's as much. Otherwise the ips is likely gonna give you a nicer picture in the light.
The viewing angle is better on the Alienware's one, having a VA screen myself it's nothing too bad.
Something i hate about samsung's monitors is that almost all their power cables are non standard, which means if you lose the cable you have to get the same, as opposed to grabbing one of the cables you likely already have for other monitors. Also they have a power brick in the middle, which can be hard to work with if you have a standing desk.
So here have those considerations
Also if you want a tool to compare monitors: This site is good to compare, unfortunately i couldn't find the same samsung monitor