Why would it need to be an SMPS and why would it fail more suddenly when
it goes compared to just a plain old transformer? I would ASSume that
since it needs to deliver 210 watts just a plain old tranformer would be
cheaper than an SMPS hence more profit for the manufacturer



210W at 12V is a *big* transformer, that's close to 20A. A transformer
of that capacity would be very bulky and expensive, most equipment these
days uses switchmode supplies because they're in fact much cheaper, they
use a lot less copper and iron. The SMPS that halogen fixtures use are
very cheap, they're more like light dimmers and put out a nasty waveform
that looks like 12V to an incandescent load.

Magnetic transformers will often smell bad for a while as the winding
insulation breaks down and turns short. SMPS fail suddenly when a
component shorts.