Stair climber vs. incline treadmill

My hill climbing sucks. I need to get my legs stronger. I own a treadmill. Will that be helpful enough to strengthening my legs on an incline setting? Or should I sign up for the gym a mile down the street that has a stair climber?

 

Not sure what you mean here. ”Strength” is rarely a big part of being a good climber. Look at the guys doing well at the mountain stages in the big tours. Skinny, small guys the lot of them.
So unless you’re running out of gears, odds are what you need to improve your climbing is more aerobic ability. And/or less body weight.
The kind of exercise that improves aerobic ability can pretty much be done on any machine. Simplified, what you probably should be looking at interval training. Fairly long intervals. Several minutes just below threshold.

 

You also didn't mention what type of hills. How steep, how long. Climbing is power to weight ratio but also endurance especially on sustained climbs.