Force Powers not working?

I've been wondering about this for awhile. Does the Darkside force powers work on other Jedi? If so, why didn't Vader just Force-Choke Obi-Wan at the end of ANH? I mean, I guess he wanted to prove to Obi that he was not the pupil that he remembered anymore and all, but still...

 

There's probably a "counter-spell" if you will against the force-choke, which Obi would probably have figured. You know, Yoda even figured out a defense agains Sith-lightning. Also, Darth may have wanted to take Obi down in a fair duel, me thinks. He wanted to show he could be boss without resorting to any cheap tricks, at least right at first.

 

Yeah, plus it would have made obi-wan look pretty weak dropping his lightsaber and gasping for air. I want a real lightsaber..

 

I suppose that depends on if Vader's strength in the force would be able to overpower Obi-Wan's force abilities.
Kinda like on Spaceballs: "He got the upside, I got the downside. There's two sides to every Schwartz"
But aside from that I think Vader would want to prove that he's the better saber wielder and beat him in a fair fight. Just to show that he's now the master.

 

I am sure there is much more going on in that fight than you can see with your eyes (or would be, if it was real )

 

I think Vader still has some honor when it comes to dueling another Jedi.

"Escape is not his plan. I must face him... alone." That is what he says about Obi on the Death Star.

Then on Bespin, he could have had stormtroopers get Luke and capture him. No, he fought him one on one.