When it comes to form and appearance, I think the ugliest tank of WW II is that Polish tank that they had at the beginning of the German Invasion in 1939. They only had a few, but the germans did them a favor knocking them all out and putting them outta our misery!
Most attractive in form and appearance: The Japanese Type 97 Advanced Chi-Ha. Even though it was worthless as a AFV, it just looks kinda 'sexy' the way they built it.
Most attractive in form and
functionality:
The Russian IS II
Most may disagree, but these are my votes.