Ha ha! I know SPANK, I remember researching it when it first came out, and again shortly before I got into VIT. I honestly think that it doesn't compare, though it is probably the most popular and the first one to become relatively well known. I remember reading their whitepaper and seeing how they dealt with the concerns of proof-of-brain and of underage performers using the login of someone else. Their idea was to have the live camera model spank herself a certain number of times when the platform told her to (random performers would be picked at random intervals). The people watching would then certify that she had done so the correct number of times and the stream would continue.
Now I'm not one of those who shouts "porn is degrading to women" across the internet, but when I read that nonsense I decided that SPANK was definitely not the investment for me!