It depends on what you value. If you are looking for an easy replacement, then Halogens are easy as the light assembly is designed to use standard Hx replacement bulbs.
Are you looking to draw less current? Maybe you've installed some accessories that use more power...so in that case LED's make sense.
Are you looking for more candlepower? Well then the choice isn't very clear cut. Sure, LED's can be brighter...but many have beam patterns that don't work well with the light assembly. It may take some trial and error to find one you like. And I know what you are thinking.."I'll just use what others have"...but quality control from batch to batch out of the Chinese factories can make each batch unique.
Is long life the goal...once again it would seem as though LED's have the edge here...but quality from budget LED's doesn't stand up. If you decided to go with LED's...buy from a name brand with an established history of designing and selling LED's.
So, which is better?