Originally Posted by ItsJustMe

Some of those energy savers are just overvoltaged. If you run overvoltage, the filament is hotter, and you get more light per watt burned. Tradeoff is shorter bulb life. Energy saver 12v bulbs are probably just made as 10v bulbs.

MR16 bulbs seem pretty durable. I have a ride that goes over 4 miles of bumpy gravel twice a day, and I used the same bulb for a year (still have it, but my primary is now an HID). So the "shorter life" may still last a year, and if you get significantly more light, it's worth it.