Andrew, I think it's important to decide what constitute an open comb and a closed comb. Most of us are familiar with the Gillette Old Type and NEW from the 1920s-1930s and would accept that they are open comb. With the advent of some of the wonderful artisan razors coming out now, I think the waters might be slightly muddied. When I think of open vs. closed comb I think of my lather catchers. Here are two examples:
This Gem lather catcher is clearly an open comb
This Ever-Ready 1907 lather catcher is what I consider a true closed comb. The comb is easily recognizable but the combs are closed at the bottom.
I get fine shaves from both of these antique razors but definitely have a preference for the Ever-Ready.
Next is a modern take on the open/closed comb in the iKon Shavecraft 101.
The open comb side of the iKon Shavecraft 101
The closed comb side of the iKon Shavecraft 101
Looking down on the head of the iKon Shavecraft 101 with the open comb side clearly on the bottom.
I very much enjoy using the Shavecraft 101 and use both sides of the razor during my shave. Both sides are quite comfortable to use.
Personally, I think the
design of the comb is more important than whether or not the comb is open or closed, especially with open comb designs.
This is just my 2¢ and others may be more knowledgeable on the subject but I hope this helps.