My comments:
I think that I am somewhat biased by my own "demi-vintage" taste, and my tendency of classification ("old endodontic box minded"
):
Group I: "Pre-Albacore hull" submarines:
Tonijn: Is one of the most solid drawings here! A very credible design!
Leonardo da Vinci and
OtsuGata2Kai: Well done drawings, both of them plenty of room for big machinery. The italian submarine with a hull form that is reminiscent of the german Type XXI.
Type XXVIIA: Another submarine that remembers the inheritance of Type XXI. Also a well done and believable drawing.
Darlin: Well done and detailed drawing, but it looks so small! I know that some research submarinas are nuclear powered, but I don´t know if a military reactor was feasible in that era for such small hull.
Hund: Another of the leading desings! A believable design and very well drawn!
Group II: "Albacore hull" submarines:
Battle II. That is my own drawing! Lacks of detail and the "master touch" of our leading fellow artists here. But at least shows my preferences in hull form!
Type O9: A nice drawing! Specially the second one (Type 09A). Plausible and well drawn.
Magalhaes: With sail, this would be the winner (for me) of the challenge! But as a sail-less design is rather "strange". Well detailed, with fabulous details as the contrarotating screws; but with odd additions as the chariot style bridge... A sail, my kingdom for a sail!!!
Challenger: A good looking hull form, but with the racked sail looks as strange as the Churchill class. Unfortunatelly is a rather plain drawing, with little detail.
Type MM: A nice hull form with a soviet like sail. Well detailed, but rather little for the machinery of the era. With a mid body torpedo set that "steals" some space in the machinery rooms.
Harushio: One of the most solid candidates for winning the challenge (well, there are others, but this candidate had the hull form and sail that pleased my own taste)!
Group III: "Post-Albacore hull" submarines:
Spectre: Good drawing, and the 4 views is an additional effort. Well detailed and credible.
Conaire: A modern hull form but with (at least!) a neat bow instead the angular prows of more modern designs. Nicelly detailed, and very well drawn and shadowed. A firm candidate for being the winner.
Naia: Also a cute drawing. And also completely believable. But as the in the Spectre ssk, the angular bow is plausible but (at least for me) unpleasent.
Group IV: "Russian like" submarines:
Darroca: Well drawn and detailed, but is so broad beamed!
Artaimis: A nice drawing, very russian, but completely credible, well detailed and very well drawn. A solid candidate!
Vortex: Another russian like ssn!, and also well done. But the free holes are to "soviet" and noisy.
D1: A November like submarine, but is the less detailed of the series.
And the Oscar goes to...
Cheers, and thanks for all the drawings.