MR16 4W 3500K 360-Lumen 4-LED Warm White Light Blub (12V)

Pros: Bright and diffused light. Inside bulb you can find LED driver - polarity not matters. Can be easily established in the holder from a halogen lamp after its small redesigning.

Cons: It is not dimmable. Cost higher than other bulbs. Radiator edges aren't ground.

Other: If you don't like to solder and don't use dimmer, this bulb your choice. Its bright diffused light will perfectly shine the necessary site of a room.

Pros: Good colour - fairly similar to halogens

Cons: Needs to be more power! Better light output would be nice but remember that 4W may present a problem to your electronic transformer.
Slighter larger that a standard halogen; a little fiddly to fit into a standard enclosure.

Other: Don't expect you can just replace your halogens with this one, but once you overcome the transformer issue, this LED globe is pretty good. Can't wait for the technology to progress so we get even brighter ones!