don't look for breed based on some sexual characteristics... for one, there are no breed standards for genital proportions. for two, you should always mind your lifestyle and living conditions and how a breed fits into it (ie: a husky is likely not a good choice if you're a couch potato or live in a hot climate). for three, it's just so shitty to think of them that way.
if somehow the general response came to "wolfdogs have the bestest pussies", would you just go and get one with (presumably) zero experience?
with all that said, the only girl i've been with so far was my kangal/gsd mixed girl so she constitutes "the best" for me. i'd like to have an xl type (leonberger or a st.bernard probably) or a rottie girl one day. xl is just my "type", i find those bulky bodies and wide heads really attractive. rotties are just very close to my heart, i never had one. i knew one girl and she was the sweetest thing. always look for attention and to just be close despite just barely knowing me. i don't know if she sensed my "zooiness" or me never being afraid or tense in any way around her. just a natural bond. which kinda hurt later on because i didn't really know "her people" (was a friend of a friend of a friend on a random garden party) and thus never got to see her again. it did completely change what i thought of rottweilers.