One thing I've noticed about so many US scholarships and grants though is that even though they partially fund your studies, it's usually only in the realm of 5,000 dollars or so, and it's never nearly enough to cover all the expenses by itself. Even with partial funding it's still pretty expensive, especially considering that you are usually spending two years rather than one to complete your degree. That ends up accumulating especially considering the costs of living outside of the typical university expenses.
If you plan on taking out loans to pay for your study, you are still eligible for FAFSA Direct Plus loans even if you go to the UK. All three of the schools I applied to had a FAFSA code. Since the cost of tuition for only a year long program over there is about the same or even a bit less than out of state tuition at a public university, you could really end up relieving your debt burden by quite a bit if you only need a year to complete the program. The costs of staying in-state would probably come out around the same as far as tuition fees when spread over two years, but anybody who lives here in the state of Florida probably has an idea of why it may not even be worth saving money just to spend any more time living here. This probably applies more to people who aren't as certain they'll be receiving any kind of significant scholarship/grant/assistantship support though, I will admit. But I feel like there's even a kind of financial benefit just in being able to save a year. That's one year less that you have to spend out of the job market or out of the hunt for a PhD program. Like I said though, it isn't necessarily the case of one being completely better than the other. Different strokes for different folks I guess, depending on whatever circumstance they're in.