I'm basically an all-leather-saddle kind of rider, and have been for many years... but I have ridden too many wet brevets where I just got tired of the combination of wet clothes and a wet saddle. A wet leather saddle doesn't fit the same as a dry one.
So I started using a Cinelli Unicanitor CMX saddle, which is a hard plastic shell with a steel frame, currently available for around $50. The CMX is a little wider than the traditional Unicanitor saddle. Pretty close to a standard B17.
[edit: I read online that the Unicanitor CMX measures 27 x 15 cm, which is shorter and narrower than a B17 Standard.]
The plastic in these seems to vary; some are harder than others. I don't know why that is.
I got a blue one last spring, and my first thought was it was too hard, so I cut an "imperial" style hole in the top:
After that I shaved down the top with woodworking tools, and eventually ended up with this:
I put thousands of miles on that saddle, including a 1200 and a 600 and a lot of shorter rides, and was very happy with the saddle, even when it was wet.
So recently I got another one, which (new) looked like this:
Again I've shaved a lot of plastic off the top, completely removing the Cinelli logo... after a while it looked like this:
I haven't decided whether that one will need an 'imperial' cutout.
I'm pretty happy with these generally. They breathe well enough, with the perforations, and they feel pretty much like a leather saddle. As with a leather saddle, I ride them with no padding in my shorts.
There are a lot of older saddles of this kind, some of which are quite good, others not; they are copies of the original Unicanitor, so narrower than the CMX one. I have one that I think is a Unica-Mex (there's no writing on it) and it is quite comfortable. I had an Arius one as well, but the plastic cracked. This isn't my photo, but you get the idea:
