Longer cranks equal more leverage.
The only negative is a less efficient stroke, or awkward reach, and that really is dependent on how you ride, how you articulate on the saddle or how much time you spend out if it. Longer cranks give a much greater pendulum effect that can influence the motion of energy.
You might find with standard ratios you are not quite hitting the 'sweet' spot.
Personally for climbing, trials, high BB and long crank works.
On road, short and sweet.