Look at what the pro's use for climbing. Set your bike up like a roadie. Use traditional drop bars and hoods.
Bullhorns are great for short climbs but for long ones, they put you in a position that is too low. I use 46cm road drops with fakey brake hoods. This gives you the most hand positions and a more upright position for long climbs. For the short climbs you can still climb in the drops.
As far as bar width, this is calculated by the width of your shoulder blades (???) I believe. I am 6'5" and am one of the few people who actually need the 46cm (c-c) width. I also broke my scapula a few years back and the wide bar helps with the discomfort. But like everything else, everyone has a different opinion on this subject