You'll get different opinions as to what's the best Luke FX out there, but I think the majority will probably tell you the Luke ROTJ is the best one. My advice is: go for the Luke ROTJ. They're getting rarer and more expensive, though - so get it soon.
As for the Vader, you really can't wrong with either the newly released ANH version or the ESB version. They're both great FXs and their hilts are VERY accurately sized. If I had to choose one for you, however, I'd say the ESB Vader. I just like the ESB look better, but that's just my preference.
What you may want to do is go read some of the reviews of the MR FX sabers on this forum - in the MR section. Every FX that MR has made is reviewed, so you'll get a good idea of what members here think of each one.