All kidding aside, it's a combination of things.
The faculty is amazing. I'm desperate to work with Bonnie Wheeler, but there are a lot of other profs there with work that interests me also -- Dumitrescu, Sudan, Neel, Foster, Moss.I favor small student-faculty ratios. Though small programs generally have fewer resources, often students will get to work more closely with faculty and cohorts. My background includes an undergrad from Wellesley (my biggest class was probably 30 people -- and that was a 100-level science class!) and a graduate degree from a program with a 1:1 student-faculty ratio.The funding is good, and medical benefits are key for me. Since I'll be leaving the work force to reenter academia, I'll be losing a job with excellent benefits, and SMU's financial package will help compensate for that better than some other places.As a small, selective undergraduate college, SMU has a good student faculty ratio for undergrads. When you consider that part of your job as a PhD student is to teach undergrad classes, that can make a difference in both your work load and the quality of discourse you can expect from your students.And did I mention Bonnie Wheeler? And the Med/Ren program? And the Dallas Medieval Consortium? Yum!
The newness of the program means that while it doesn't have the clout of some other places, students will have more ability to help shape the program than elsewhere. I earned my master's degree (in Education) from a program that was similarly new, and it's grown into a solid program. I guess that experience has given me confidence in new programs. The big concern, I think, is placement. That's not something that a graduate student at SMU is going to be able to judge right now. However, given the caliber of the faculty, I suspect that SMU grads will do well. I also believe (perhaps erroneously) that it's less about the name on your diploma than what you've done during your time. A posh name might open a few more doors initially, but it's not the only factor.
There are also some lesser points of interest for me. I think Dallas would be a great city to live in. I'm Buddhist, and Dallas has a surprisingly strong Buddhist community. Dallas is for geeks; I make no apologies for being a geek and loving roleplaying games, and Dallas has geek resources. Despite being known for its oil industry, Dallas is actually very eco-friendly, which is important to me. Housing is also an important factor for me, and the average home sales price in the greater Dallas area is only about $100k currently.