Originally posted by Lightsnake
IF by 'trained' you mean 'given basic instruction' then....
Weaker than Vader or no, he certainly got the better of him there. Vader was stronger than Kenobi and we see how this went. I'm sure Yoda would give his last hope basic training and not actually fully educate him on the Force.
Lets see:
When Luke goes into his rage attack, he basically charges at Vader swinging his sabre from left to right, like a madman. Vader does not take advantage of Luke's rage and feebly blocks him, whilst intentionally back peddling towards a nearby railing. Vader reaches the railing, quite deliberately falls over and then sits there, holding his sabre up quite weakly.
Luke then chops his hand off, gee anyone could do that.
Luke's victory is more a reflection on Vader's redemption rather than an actual fight.
Vader stronger than Kenobi!? WTF? Vader is less powerful in the Original Trilogy than he was as Anakin Skywalker in the PT. Not only that, did you miss the part where Obi-Wan turns off his lightsabre and lets vader hit him!?