Hi mm, me again...

Most dimmers (esp the reasonably priced ones) just stick a resistance
in the line. So, they get hot (hence need a little ventilation, esp the
high power ones). This consumes a fair bit of electricity. The smaller
bulb w/ no dimmer is definitely more efficient. I think there are fancy
dimmers that are electronic and chop the phases or something, but these
still won't be 100% efficient.