Everyone has their own favourite style of capo. I love shubbs.
What's perfect about a shubb?
It's small, it's precise, it doesn't get in the way, it holds the strings evenly and firmly, it's quick to place, you spring it after you've placed it (ie you are not holding the spring in tension while lining it up); it's adjustable, there are several different models with different curvatures for different types of guitar neck.
All in all, it is a perfect piece of micro engineering.