First off, I am not subscribing to point "which is better" in general. It's only "which is better" for you personally.
So here are a few thoughts on "what is different" about these two programs.
Just as you indicate in your own profile, Smith is heavy on attracting applicants with IT background. So if you want to stay with IT industry, a lot of your classmates will be from the same experience pool, which could be beneficial for your post-MBA networking. McDonough has a more diverse students pool from what I could see after visiting information sessions, open houses and doing class visits in both.
McDonough borrows a lot from its parent university reputation, which is probably the highest in DC area. Therefore probably better perception of the university association in our region. Same goes for alumni network.
All part-time programs of Smith are held on sattelite campuses. Hence, less access to faculty outside the class. Most likely more classes are taught by adjunct professors, and not by those who built reputation for full-time Smith MBA. Smith is spreading itself very (too?) thin with 3 part-time locations in the area, and none of them on main campus. McDonough just opened their spanky new business school building last year.
McDonough will cost you more, because they require more credits for graduation than Smith, have required international residence, and cost per credit is slightly higher.
I have a post in my blog, which touches on comparison of DC-based part-time program from slightly different prospective. Check them out to learn a bit more: http://parttimembadegree.com/2010/02/14/gmat-test-2/