Personally speaking, if you want anything related to policy research, MPP is a great program. Also, UChi is good for academic/research training. You actually don't need to worry too much about the extra tuition because the second-year students really have a lot of chance to be student assistant (I mean TA...) all well-paid, and waive a great amount of tuition! But if the program is one-year, you don't have a chance to do this. So, I recommend you to choose Harris.
Also, when it comes to career service/academic advise etc. Harris is way better because it is an actual "school" with a lot of resources! while Columbia program's career service or any other support seems ... a little too weak.