While I agree on the other points (schedule etc),and while the product itself is a no competition situation (not that it really matters for this hop), I fail to see how SQ’s gates at KUL (Satellite) are better than MH’s (Main terminal for 737s) for someone looking for a quick hop to/from KUL- the 5 odd minutes that it takes to get to/from the Satellite- if the train is working, add a good 10% or more to your travel time.

OP: You’ll be fine with either MH or SQ. CX will Interline across tickets to both, and the bus transfer T4->T2, while a pain, will be easier than claiming bags at SIN, rechinging with Air Asia, and dealing with the hassle that’s the KLIA2 experience.