its simple.. those areas which the SMRT feeder/ intratown serve
are very high density areas and most of the times, there is only
that one feeder bus plying into the road, so need bendies..
unlike SBS, some parts of the town are served very well by feeders
and trunk services, such as Toa Payoh, Tampines, Bedok etc etc. in
many parts of woodlands and yishun, some roads only has one feeder
plying one entire stretch of road, same case for sv365 at
BB..
and since ppl says SMRT dont have that much spare buses to play
with, that means longer frequency.. in turn means using bendies to
cope.. SBS use regular 12m buses but the frequency is very
good.
note that for SBS, only mature estates feeders have good frequency,
like bedok(222, 225), tampines(291 293), ang mo kio (261, 265,
26
and yes.. 911 912 913 frequency is very bad, esp 911, evebn when
theres on jams