As said, the problem with trekking bars is you pretty much are forced to sit on one plane, with a little variation in the reach and hand position. Tough on your back and butt. They are also heavy, you'll feel it, and definitely non-aero. Drop bars allow you to rotate down and stretch out. Aero bars give a nice stretch option, but I can't use them on anything but smooth roads with a good shoulder.

I like my trekking bars on one of my LD bikes, but wouldn't recommend them to a friend...it's a matter of preference and an odd pick. On a 8-10hr ride, I'll lean on the trekking bars and use them like aero bars for a stretch, but ain't so comfortable.