Hi Susiesan cant tell you much about Borneo but can tell you a lot about SL. SL has the culture, the wildlife, the beaches and shopping. Most hotels in SL will cater for the Western Palet. I am from there but based in Sydney, I am actually off there next month. Feb/March is still good on the South Coast for snorkelling and diving but personally the Eastern Coast is a lot better but a lot less developed. But the beaches are amazing. The hill country where tea is grown is also fantastic. Contact me and I will put you in touch with a SL travel agent that I use. Driving in Sri Lanka takes a long time...there are some areas you can now fly to via a Air Taxi.

However if you want to see the country nothing beats a road trip. In Sri Lanka the luxury chain hotels are yet to set up, You can get some very nice places for a 100-150 per night BB basis. Sigiriya is quite an easy climb, Adams peak on the other hand is one the hardest climbs I have done..you start your climb about 2am to make it for sunrise, which is spectacular. Your best way to get to SL are following, I have noted the main alliances:

Korean Airlines via Seoul.
China Eastern via Kumming
Cathay Pacific via Hong Kong
Malaysian Airlines via KL
Ethihad via Abu Dhabi
Emirates via Dubai
British Airways via London Gatwick and Maldives
Royal Jordanian via Amman.
Singapore/Thai via their respective Hubs.

Have you considered using points one way and purchasing a ticket one way. Business Class airfares are a fraction of the price out of Colombo.