As much of a fan of DELL as I am, I would honestly have to say neither right now. They both have problems right now which I guess is to be expected as they are new products. DELL I think pushed these out to the market too soon without  proper testing and it appears their QA is lacking. I would wait awhile to see what they can do to fix the problems. Keep reading the forums and then decide.

I read alot of negative things about the R3 but bought one anyways...like I said, big DELL fan and it's an Alienware. I have had no problems with it at all. Of course I bought ut way after the intitial release. Good luck and take your time before deciding

I chose the Aurora ALX. Mostly it was because it looked better in my opinion and also because of the cost. The Area 51 typically has more "hardcore" components and has more overclock settings. With the money I saved on the Aurora I can pretty easily upgrade my video cards and Ram over time.

Think of it in terms of room inside the PC. The X51 is a micro chassis. This limits it's abilities and expandability. Space inside the machine is one issue and the second is your power-supply. The largest available is 330 watts. This restricts how much and what items you can put into the system. If you are serious enough about your use, the Aurora is a far better choice. Even it is limited by a small power-supply for a gaming computer. More importunately is the fact that it only has two PCI 16 slots. It has a limited ability to upgrade for any serious gamer. If you are looking for the higher end gaming computer then Alienware is no longer your choice. If you want a nice system that can run one high-end video card then the Aurora is an excellent choice. The X51 would not be my choice for a gaming PC.