I’ll start. Canine, nothing beats a knot. Totally unbiased here ;).

(Cropped from Aycee’s “Safeword” comic at https://www.furaffinity.net/view/20692415/ )

Canine, definitely.

Tier List!

S: Felkin, Dragon (Hemipenes)

A: Canine/Lupine, Dragon (Knot), Lizard

B: Horse, Crocodile/Alligator

C: Lion, Minotaur

D: Avians, Human

Dragons generally just obliterate the competition here becase much like other reptiles, you’ve got some incredible variation in how a dragon dick gets designed and you can load it up on insane frills and tiny little spikes that would feel very good rather than sharp. Also hemipenes are really unique, and I prefer them to the knotted dragon-dicks because they can be used in more ways and also mean that it actually makes sense to hump right until the end, instead of just slotting the knot in for all of 3 seconds during an animation.

Canines score extremely highly for obvious reasons. However… They lose out to Felkin here, which get all of the knotty goodness of Canines and then combine that with the awesome girth and load size of a horse, adding in some very impressive balls for good measure.

Lion could score better if their junk was naturally bigger, but alas. Gotta upsize it a bit for any art.

Canine: Knott me baby one more time