September and October will be rainy season in the Philippines. However, they have lots of beautiful beaches there with white fine sands like Boracay. Palawan is a great place as well, they have the Underground River that was considered as one of the New Wonders of the world. Bohol is such a peaceful and wonderful place in Phil too, they have the beautiful Chocolate hills there and a beautiful beaches. People in Philippines are so friendly and hospitable. There's a lot of fine restaurant and hotels as well which is very cheap.
Hope this gives you an idea when you travel to Philippines.
Had been to Sri Lanka in Dec 2012 for a short 4 day trip (route: Airport -> Sigiriya -> Kandy -> Pinnawela -> Negombo) and we enjoyed our travel. It is a very small country, smaller than a typical province in India, with a lot of variety, so would be quite easy and economical to traverse. There are beaches, hill stations, cultural attractions and historical ruins and all quite close to one another, so you wouldn't need to spend a lot of time travelling.
Also, if the idea of relaxing on a small Indian ocean atoll excites you, check if you could include the Maldives too. The island group lies to the west of SL and there are flights to Male from Bandaranaike Airport, should be a short 1.5 hr journey. However, do note that Maldives is mostly focused on resort based tourism, most of the hotels are actually resorts, each located on a small island.
Thought I quickly report back from our trip. Our three weeks in Sri Lanka were fantastic for all sorts of different reasons and I highly recommend to visit the island. Feel free to drop me a line for any advice in case you plan to go.