Can't answer this for you. I don't have funding from either school, so my decision is quite clear. But here is what I felt from my search on both schools- HKS has the greater brand, but SIPA courses are outstanding! (not that HKS's courses are not). It's one of the few schools to have such a vast array (really vast) of courses, at least in local and state finance and political management (what I am interested in). So would recommend you compare what you want to study and recognise people you want to work with at SIPA. There are lot many more students at SIPA than HKS, but then there are also many more instructors/professors you can work with.
On Salaries, the pay is lesser (by few $'s) at SIPA after graduation, but with half the loan as HKS, it will hurt you lesser. I am sure career progression will depend on where and how you work post-graduation, rather than just the school brand.