Long vs Short...
 

....hills :)

I have a few hill options around my parts. The bridges are a few hundred feet of climbing but over a mile or so. Then there are a few steep hills but are pretty short.

Which is better to train on?

What are you training for?

Getting stronger, losing weight, more centuries. I always hear 'hill repeats' and was curious what you guys do.

Go to the big hill in CP, ride up, make the first left on the way down. It cuts back to the section before the sweeping downhill that leads to the big hill. Repeat as often as necessary. Once you get bored of that, hit River Rd.

edit: Get some clips and straps or powergrips (or clipless). It makes climbing easier.

I was thinking the Great Hill. Also some stuff up in Inwood Park that's pretty hard.

That's interval training. You probably want to do some research on this, because it's a good way to get hurt if you don't do it right. You also need a good base of aerobic fitness before you even get started, but if you're already doing centuries, you're there. As for long vs. short, it's the length of the interval and the recovery that matters -- the hill's immaterial. Do a websearch to get info on interval training for cycling, start with a beginner program, see what it does for you. Oh, and you don't want to do interval workouts every day.