(Answered this since nobody has and I felt bad! Hopefully some of the seasoned people on here will chime in. Below is my experience with stairs...)

In the past I worked for a bodybuilding company and we ran the stairs at Red Rocks in Colorado. I remember not being able to walk in between very well. I don't do that anymore since I'm older now and I prefer less pain.

I think you'll have to experiment for boredom/results. I have done two different things in the last year...

--Perform my entire lower body lifts and finished off with 5 floors up and down. It kills me.

--Randomly get up from my desk every couple of hours and do 5 floors up and down on top of my regular weight workouts.

Anyway...more frequent stairs (2nd example) did hurt my knees but I noticed a lot more soreness in my calves, ankles, knees--both anabolic and tendons/joints soreness.

I prefer just doing the stairs now once a week after lower body weight training--I think it fatigues the muscle more and gives me tabata/HIIT-like results without having a catabolic effect (leaning out.)

I would say the weighted stair climbing is just pretty freakin' cool and studly. Your quads will hate you.

In any of the scenarios I would say less is more...coupled with some weight training and slow walking or sprints.

If you are just trying to increase your athleticism for soccer then I say more sprinting stairs but you may sacrifice some muscle.

i used to run stairs on my lunch break at work. i would do 3 sets of 5 stories up and down with 40 pushups at the end of each set every weekday. i walked down, being mindful of fighting gravity with each step. i never experienced any knee pain.
when i first started, i employed a strategy of 2 up/1 down- 3 up/1 down till i was able to do the entire 4 flights up at one run. then i worked on speed going up.
be careful with the added weight. i wouldn't attempt it till the stair run itself is no longer a challenge.

I've done it both ways. At my office I have access to a stairwell of 29 floors. I worked my way up to climbing 4 times in a lunch break. I'd do that 3x per week, sometimes all 5 days. It was great for building up my cardiovascular capability.

Later on, I started doing sprints. I'd climb the first 5 floors, and then do sprints of 4 floors a piece. I'd double-step while running and get up the 4 floors in about 20-22 seconds. I'd then wait until my heart rate came down to ... something. Usually 125 or so. Then another set of sprints, repeat until I got to the top.

As far as which is better - what's your goal?

I was doing IF and fasted stair climbing throughout, and I think I lost more fat with the steady climbing. But then again, I had more to lose when I started. And after all, the total time in the stairwell was easily 50 minutes or so when I was climbing 4x29floors vs. 15 minutes (including all the rest time) for the sprints.

And I've descended a lot of those flights of stairs with no damage to my knees detected. (I could only get in and out of the stairwell at the 1st and 24th floors, and I used to like to increase my floor count in increments of 5 (because I'm nerdy like that) so I'd have to do a lot of descending some days. To do another whole set I'd descend from 29 to 24 and take the elevator back to 1.)