I think WBVA is much more boxing oriented, MMA-Tracker has some boxing, but it's much more MMA oriented.
I'm not a member of MMA-Torrents, but I know MMA-Tracker is much bigger in terms of content. I can assure you that there are lots of instructionals there, from MMA to BJJ, Muay Thai and kickboxing. There are fitness training programs too of top of the multiple matches releases they have in multiple leagues and countries (UFC, Bellator, Brazilian leagues, Japanese martial arts etc.)
If i'd only have to choose one i'd go with MMA-Tracker, but that doesn't mean the other two are no good![]()
Hope this helped,