Public Bus for me.
There's always (or most of the time) seats for me when I take buses
during off-peak, but not for MRT during off-peak, I even had to
stand most of the time. 
On buses, if one isn't sure of the route, he can ask the BC/SC for
directions. But on MRT except NEL, if one is unsure of which
station to alight, he can only refer to the map diagram or ask
other passengers. There is a lack of communication between the
train operator and the passengers.
MRT has fixed route (track) to run, but for public buses, just by
twisting the route can make the bus goes to another place the
service has never ply before, and it's another good time for me to
explore around. 
