downlights that is.as far as i can see 12v cost less to run but are more expensive to buy and theres more to go wrong. and why do the prices differ so much for 2 items that look pretty much identical??
50 Watt halogen 12v and 240v cost the same to run. In my opinion you do not get the same light output from 240v halogen and customers say the bulbs do not last as long. I fitted 4 lv downlights in my daughters bedroom five years ago and have not had to replace a bulb yet. You can have problems with the fire rated fittings though. i used to fit ibl but have had probs with lampholders burning out. If i fit lv these days i use snaplite. But i tend to be fitting jcc low energy downlights more these days.
In an office that i do maintenance on , they have about 35 240v GU10 downlighters, and i am regularly replacing lamps,after only a few months, where as elsewhere they have 12v lamps and they seem to last at least 3 times as long.