I see that, briefly, the rationalization of the old man vs. the machine was used in this conversation. I have to say that's one of my least favorites. Thankfully, this thread moved on to users' preferences, because that's really the only way to gauge the fights. I pretty much agree with a lot of what's been said here. Empire's duel is my favorite. It always has been since the first time I saw it. It always felt the most real and the most grueling. Jedi's was good too but in a different sense. It has an emotional resonance, but since Luke refuses to fight for most of it, it doesn't have the same sense of action that Empire's had. I also enjoy watching the prequels' fights because some of them do look cool, like in TPM. I even enjoyed Vader vs. Obi-Wan, although the balancing on various bits of metal at the end broke my suspension of disbelief completely!

But the fights of the two trilogies were created under two totally different mindsets, choreographed by different people, and they just don't mesh together. It's up to the viewer's preference if they prefer the more down-to-earth, grueling battles of the OT or the flashy acrobatics of the PT. But to try to rationalize why the fights in the OT didn't look like the fights in the PT because of the old "Ben's an old man, and Vader's a robot" is just silly, especially because, even though George coined it, he largely ignored it. Let's explore:

Ben's an old man--Yes, but there are old men characters in the prequels: Dooku, Yoda, and Palpatine.

Vader's a robot--Somewhat, but there is a mechanical construct in the prequels: General Grievous.

And, guess what? All of those characters are constantly seen jumping around like they have briars up their asses, so... how exactly does this argument hold water?