If you've to change 3 times, the hotel is 1km away from the subway, your party is 2+ people, you got a luggage to schlepp and it's during rushhour (especially in a direction that the taxi will not be affected by it so much) - or at least couple of those factors - I'll definitely agree a taxi is the way to go.
But if it's an easy 1 interchange, hotel nearby the nearest subway exit, you're a single, seasoned traveller with a light / easy to carry bag, then I'd go with the AirportExpress/Subway combo. It's really down to your personal situation what will be the best solution.
Remembers me when we arrived as a group of 5 in SIN.
Me and a collegue decided to go with MRT, 3 collegues went with a taxi.
MRT went fine as always, with a quick connection at Tana Mehra and straight to the hotel it took less than 40min. Collegues were stuck for about 2hrs due to an accident on the ECP. I think my pictures of us enjoying food and some Tigers while they were squeezed in the jam didn't made their mood better
