My most comfortable position is on the brake hoods of my road bike.... so I bought bull-horns for my other bike. It was then that I realized when I go on long rides, I like the roadie bars because of this....
Hand's on the flat end of the drops
Hand's in the curve of drops
Hands on the brake hoods
Hands on the "shoulders"
hands on the flat part
(not at the same time

)
Many positions for my hands, and I can twist my arms all different ways, as well as move my back a little.
I also have aero bars, but have used them less and less as I ride with more people. Not so comfortable for long distances either... atleast for my back.
I've never been into mountain biking, so I know nothing about bar ends... maybe those will give you some diff. positions also.
Have fun, before you know it you'll be doing centuries.