Personally I would take the day from LP rather than SR as suggested. But I agree that it depends a bit on how much you enjoy the temple hopping. There are lots and lots of temples. SR is not just Angkor Wat. And like I always say, it's the tropics. Don't expect to do as much in a day as you might in more temperate climates.

I liked Hanoi. And also took a couple of interesting day trips from there as well.