I can only speak to Sri Lanka but can say that I liked Galle (colonial city that was still more of a lived-in place than a tourist reconstruction), Hikkaduwa (for beaches) and Horton Plains national park a lot. Kandy was oversold IMO but worth a look. Didn't make it to Polonnawura and Jaffna was no-go at the time. Colombo had a bad vibe from physical defenses against Tamil attacks, but I'm sure that's eased now. Staying the the Galle Face Hotel right on the Indian Ocean coast at $21/night was pretty amazing. The nicer parts of the city can be pleasant, though the Pettah is a reminder of what so many have to live in.

You could easily fill a week.