Both programs belong to post-professional degree, which you need to have a some sort of professional degree to start with. M-Des is one year and you need to pick your concentration field when enter. YOU WILL NOT GET STUDIO CLASSES IN THIS PROGRAM. Acceptance rate in this program is very high, due to no studio, you will not get a desk in Gunt Hall. I personally think this is just a money making program for the school. On the other hand MLA 2 is a post-professional degree, which you will need studio and it is one of the hard core program in design school. Acceptance rate is very low. Hard to get in, but this is a real deal in landscape design. Wish the best on your application.
Oh, sorry to mention this, most programs in graduate school of architecture, specially GSD, counts very heavy on the portfolio. They are looking for orginal thoughts of works, like paintings, drawings, and any art related creative piece was done by your own creation. So, try not to put professional job works from the office into your portfolio, unless the job was totally done by you.