Hello! My name is Kate and I currently attend KCL for the MA in Terrorism Security and Society. First of all, congratulations on your offers - both KCL and UCL are great schools! I also received offers from both schools, but settled on KCL because of the programme and the international reputation of the War Studies department. In terms of the degrees you are considering, the IR MA at King's is relatively unmatched in terms of providing a superior education. I have many friends in the IR programme, as well as friends from past years who did this programme, and the vast majority are either continuing their education via PhD programmes at KCL, or are well situated in a 'dream job' atmosphere, which tells you a lot about the education provided at KCL.
However, something to definitely consider is the type of programme you are looking for. An IPP is inherently different than an IR degree. IR at KCL is heavily focused on international theory (realism, liberalism, etc.) whereas an IPP may be more focused on policy formation and implementation (I don't know this programme, but I would recommend knowing the differences!). You may be able to take policy-driven optional courses at King's, but the IR core course is essentially IR theory (we all get to take 2 optional modules alongside our core, so there is definitely possibility here).
In terms of what programme is most well-regarded, I don't know that you can go wrong. I chose KCL specifically for the design of the Terrorism/Counterterrorism programme and for the international reputation of the War Studies department and as a student from the United States, I wanted to make sure people from back home would know the type of education I was receiving (KCL is one of the most well known in the US for anything intelligence/IR related). I would suggest choosing the programme that interests you most! I hope this was helpful.