Both of those system's look great to me, but to help you pick the best one for you we would need to know what exactly you use Maya for (Texture Artist, Animator, Simulations, etc).
In my personal opinion, the Alienware will serve you better. You get the same memory configuration with the exception of ECC which to my knowledge doesn't help Maya too much (I've never used it and don't have any problems). The real difference in these machines are the processor and GPU's.
The AMD gives you quite a bit of RAM and adapters, but that much in my mind is only useful if you are texturing everyting at 16K+. Also, AMD hasn't always had the best dedicated drivers for 3D apps. The 2 980 Ti's will serve you plenty well (just disable SLI if you don't game) and you have a very powerful workstation for GPU rendering if you're into that (I personally love Redshift, blazing fast with CUDA). That's another advantage of the GTX cards, you get to use CUDA accelerated applications with them as well.
For the processors, I would also go with the Alienware and it's i7. The Xeon may look like a great deal, but the 26xx series are designed to work best in dual cpu configurations. The only times I would buy a single Xeon are if it's a 16xx (only allows 1 CPU), where it's a better quality i7, and still overclockable, or if I knew I was going to get a second 26xx down the road. If it's just one CPU, the i7 should annihilate that Xeon in any rendering/work tasks, single threaded and multi-threaded.
Above anything else, make sure you have a proper disk configuration in the system. I would recommend an SSD for boot/applications, a large HDD for storing past projects and media files, a fast SSD for working projects (probably around 250/500 gigs for multiple large projects), and maybe another SSD or RAID0 setup for cache files (I use these to store nCache and Fluid bake files, as well as files from AE/PP/Nuke/etc). I'm no pro at disk management, so take this with a grain of salt.
BUT, if you are a texture artist working in extremely high resolutions, maybe that Precision is for you 
-MR