A trike is great because you can climb a hill at whatever speed you like, and not worry about falling over.
As far as 2-wheel bents go, the one I hear mentioned over and over is the Lightning P-38. Something about the triangulated frame and the seating position makes sure that all of your power goes into spinning that rear wheel. Of course, there are lots of other great climbers out there, and the thing you should look for is a nice, straight chainline without significant direction changes, and no "air gaps" that could turn the bike's frame into a spring when you're cranking hard.