Aside from the incoming avalanche of double entendres, I like my Slant barberpole and my Muhle R89 (ej de89) as well. I will be able to comment on a Muhle 2013 R41 shortly.
I didn't like the Feather Popular, not because it didn't do a good job, but because of the light weight/plastic it didn't "slide" and I felt like I had to drag it for most of the shave. Between the mild razor burn and having to shave like a regular plastic razor and not like a metal DE, it didn't feel like "my razor." I would expect the metal Feather AS-D2 to not have this issue.
My Merkur 1904 open comb had a very elegant looking design and the open comb had a nice gliding action, but for me the "blade right on the open comb" design was irritating and also didn't shave closely at all. So my vote would be against that one.
For overall design, an open comb or "teeth" like a Merkur Slant that doesn't wipe the lather away before the blade strikes me as a good design. The idea of a slanted/guillotine like blade that is more rigid and less susceptible to flex also strikes me as a good idea. Lastly, the concept of a shaving razor head that doesn't have the blade protruding past the imaginary line that connects the cap and comb/safety bar also strikes me as a good idea - I saw a Muhle R41 2011 in cross section and the darn think looked like a "weapon of mass destruction." Yes, I expect the Legion of 2011 R41 to hunt me down for that one!
Beyond that, a small razor head for maneuverability.
So far my Muhle R89 has the nicest performance. Shortly behind is the Fat Boy. Surprisingly I didn't like the Slim adjustable as much at first blush, and I really thought I would. My only complaint about the Muhle is it's a bit hard to get under my nose. I have to go up against the grain to get close enough. I don't mind that, but I thought the Slim would be a better performer, but I haven't been able to get an irritation free shave from it...yet. I need to find the right blade and setting combination.
Lately I have been enjoying a late 1950's British made Rocket. Although improved technique must have something to do with it, I have recently been getting some of the best shaves of my life. Fantastic design.
The Rocket head is very good indeed, but the first place would go to the Mühle R89 head, in my opinion. I think the Mühle / EJ designers produced a head that is both extremely easy to use, and is very effective.