While some individual ships in Warship Girls (zhan jian shao nyu) have cool looking art, overall I find the art direction in KanColle much better.
It depends on your personal preference (Your preference and opinion is correct) For me. Warship Girls arts are far more interesting (KC artwork is excellent make no mistake) while its destroyers are not as mundane and similar looking as KC destroyers particularly the Fubuki Class where most of them look very much the same (though Fubuki class destoyers in warship girls also shares heavy similarities with each other)
Warship girls shipgirls arts has more "individual" feels as each one is unique. If I have to compare Kaga and Akagi in KC, I may be wrong but besides the hairstyle and the clothing color they look very similar. For WSG Kaga and Akagi despite the same style of clothes they have very unique appearances lookout that "differentiate" them. Examples include WSG Kaga's hair color, preference for sake and references to Kaga city in the sake bottle while Akagi holds her bow with her right hand because of the island superstructure added after her modernization but lack of reference to its regional namesake (No reference to Mount Akagi where IJN Akagi got its name). WSG Akagi's clothing is good but I will admit that she looks too similar to KC Akagi. The "individualsitc" artwork is done to create a more unique identity and personality per ship girl through art as WSG don't have voice acting to "express" their personality through voices.
But like I said, it is your preference that matters. Some prefer KC's art direction while some prefer WSG's. Doesn't matter.
Shibafu is exceptional among the Kancolle designers. ^^;;;
Besides, there are also individuals who love the style because it's not "mainstream moe"
Like I said, it depends on the person's preference.
But some peoples just like to insult some of the others' arts based on their "fanaticism" of the product. Some die-hard KC fans like to insult the artwork of WSG just because of the fact that the later is a clone (a clone that is struggling to exceed the images of being a clone) though vice versa happens as well. In the end it is not "which is better" that matters but "what you like" because it is meaningless to compare WSG and KC as the former is slowly started to show more of its unique characteristics (game mechanics, style etc) so comparing them is equivalent to comparing an orange to an apple.
I am not saying that KC Kaga and Akagi were boring or too similar. They are similar but they have their uniqueness and the artwork of KC Kaga and Akagi is excellent by Shibafu. But, if you want something besides the "mainstream moe" as you defined (though I have no idea what that means as I am not a dedicated anime fan just enjoy it once in a while) then go to KC - no one's stopping you. If you want something more "special" or more colorful then go to WSG - no one's stopping you.
In the end, it is what you like that matters it is not which is best because it would just be meaningless comparisons.
Forgive me but I disagree: Both are good in their own way (and i like them both) and there is no such thing as "clearly" in judging artworks because it is defined by your own views and preferences. Your preference for Kancolle's version Prinz Eugen is not wrong but not the "clearly is better than WSG version" as it is too subjective. If you said "clearly" it usually means that it is overwhelming accepted to be correct but that is not entirely true as judging artworks involves subjective view (there is not definite answer or view of the artwork). Quite significant number of people love the WSG version of Prinz Eugen but even I won't dare to say that WSG Eugen is clearly better than Kancolle because I got no proof but so does the KC Eugen as you cannot compare the preferences for KC Eugen or WSG Eugen from people.
Most of the time I've just so thoroughly associated the Kancolle designs with the ships in question that any other personification seems odd. Though I'm sure that many of the ships that Warship Girls did first will also take some getting used to when/if Kancolle introduces them. (Warspite is an exception in that regard because I found her Warship Girls design kinda meh to begin with, while her Kancolle design is perfection.) In particular I just can't imagine any other look for Hood than this.