Overall, I prefer Sideshow (what do you expect), but I really enjoy the one Medicom figure I have. I anticipated Vader being wonderful and he is! I keep him seperate from the rest of my collection because of the height difference, but he's a super-high quality figure. I'm not sure he looks exactly like Shaw, although I think they got the essence of the character down beautifully.
I will never buy another Medicom figure. It's not a quality issue. It's expensive! i just can't afford it. And I don't think it's worth the price, though, as I said, I am very happy with my Vader. He's easily a $75 figure, but not the $150 I paid. He's gorgeous, but I can't afford to collect the line, so I'll stick with Sideshow, which everyone knows I am VERY happy with.
I'm not sure I understand the need to contrast and compare these figures. To what end are we making these comparisons? I doubt anyone needs to mull over which figure they want at this point, and the quality of both figures is beyond dispute, whatever their individual flaws.
I'd love to paint a Medi-Luke head, just so I can see what the real sculpt is. My Medi-Vader is the ONLY figure i have that has gone un-modified. I'm willing to paint up a $40 - $70 figure, but once we get into three digits, he stays as he came! I'm even scared to throw out that enormous box he came in!!