Hi Denise,
Like Hils, I have done both tours. I loved the Vietnam and Cambodia tour from start to finish - each place visited is quite different. The scenery was often beautiful - Halong Bay was a wonderful experience and I loved the old town in Hoi An. The two countries are quite contrasting and complemented each other very well. It was wonderful to see the temples in Siem Reap but equally l loved the boat trip to Phnom Penh and the city itself. The food was excellent in both countries.
The Borneo tour had two huge highlights for me - the stay in the jungle and the add-on to Singapore. The jungle lodges were wonderful and we were very fortunate to see not only orangutans in the wild, but also pygmy elephants, as well as proboscis monkeys and other wildlife. The rest of the Borneo tour wasn't very exciting in comparison! However, I absolutely loved Singapore (I hadn't been before) - there is so much to see and do!
I hope this helps!
Bob