ohcoture

Hi martinet25.  I am not an expert on Harvard, but here are a few quick thoughts.
 
My understanding is that the MPP at Harvard is the largest of the professional masters degrees and the most generalized.  Students range from 22-year-olds with newly-minted bachelor's degrees to seasoned professionals.  There is probably something there for most qualified applicants.  The MPA is a more specialized degree, the average age of the cohort is a bit older, and many students already have a master's degree or significant economics/statistics/math coursework.  I also suspect that the career interests of the MPA candidates are a little more narrow, and more geared to analysis and policy jobs (regardless of nonprofit/NGO/government field) than the MPP, which certainly produced policy folks, but also people who go on to perform more managerial or leadership functions in a wider array of loosely-defined public service industries.  My sense is that the MPP is also a little easier to get into than the MPA, but I don't actually have any data to back that up.  Simply, they're different programs with different goals.
 
Then the MPA/ID is an entirely different program unto itself, as well as the MC/MPA.
 
I would encourage you to think really critically about what your long-term professional goals are and learn some more about the what makes the MPP and MPA career paths similar and different.  Here is where you want to reach out to career services and ask these questions directly.  What do you want to do, and which program will help you get there?  Remember that it's not just about "doing school" but investing in your own human potential to make a positive change in the world.  Which program will better prepare you to do that the way you want to?
 
[it's worth noting that at every US university the MPA and MPP degree distinctions mean slightly different things, so it's worth investing time to sort out the distinctions where the exist and not assuming every MPP is the same everywhere and wholly different from the MPA, etc.].
 
Good luck!

I think it depends what you want to do. I don't have the luxury of choosing between HKS and SIPA, but $20,000 over two years isn't insignificant. I think, between all the top programs, the benefits of one school over the other (within public service) are pretty marginal. Is that marginal difference worth $20,000 for Harvard? Maybe if you want to broaden your career prospects, as HKS has better private sector placement. HKS definitely has the better brand name of the two, but (as others have pointed out) SIPA seems to be devoting more resources to the school in recent years including a new loan forgiveness program. Harvard's program isn't actually loan forgiveness. SIPA also has a combo of tuition assistance/stipend/salary for TAships compared with Harvard giving TAs a basic wage. 
 
Also, if each city factors into your consideration, I think New York offers a lot more for the money than Boston. $10,000 almost pays your rent in NYC for a year (if you're living in Harlem, at least).
 
Are any of these degrees with the money? That's a harder question. Good luck deciding!

So here's my best understanding (though I don't even qualify):
 
If you are at the 100% benefit level for the post 9/11 GI Bill, private schools that participate in the YRP will kick in money above and beyond what the GI Bill pays for (since private schools are obviously a lot more than the public school rates that GI Bill pays). The gov't will then match those additional funds. It's important to note that you must be at the 100% level (3+years qualifying active service) and schools often have very limited slots for the YRP.
 
Example:
Harvard Kennedy School offers up to 30 spots at $7,500. With the gov't kicking in another $7,500, plus the $19,000 that the GI bill pays, you're looking at $34,000 paid toward tuition plus obviously the monthly housing allowance to cover rent and what not. 

Revolution is clearly very finance/private sector-oriented, which is fine. But I agree that he constantly questions the intelligence of IR/public policy students. I'm a big boy and I can take it but it's clear he is very driven by prestige and reputation factors. I'm sure a lot of MBA students think about MPP/MIA students in a condescending way but that shouldn't come as a surprise given how we know what kind of d-bags many of the MBA people are in real life. This is just my impression of what's going on.
 
If you want to work in finance or in consulting etc., Revolution has a point about these programs. But if you want to work in international/multilateral organizations, in the government, in think tanks or even in some segments of the private sector that require policy analysis skills, SIPA/SAIS/Fletcher etc. are very good programs, if not the best programs, for you.