From SIN-KUL (40min flight) it's always a toss up for me.
I typically fly for work, I have somebidy pick me up from the airport; but I drive when with family.
Catching a cab when the tropical thunderstorms hit in Kuala Lumpur is no fun.
The biggest problem we have here is crossing the border from Singapore to Malaysia.
Off-peak it can take 10 minutes.
Peak times, school holidays etc can take up to 3 or 4 hours.
The drive itself on a 2 lane highway can also be eventful when there's an accident. So a drive of 350km, which on good days I can cover in 2 1/2 hours (breaking the speed limit), can take up to 5 hours if I'm unlucky.
So in a really unlucky scenario, 350km end up taking 9 hours.