The most viewed thread ever on MTF is "Male Players' Bulges" ...
The reason TF has way more activity and fun that MTF is that TF has a much better vibe. It's funnier, friendlier, and more light-hearted. It isn't mean-spirited like some of MTF's main posters. The ambiance on MTF can get misogynist, nasty, and profoundly negative. You can already see the profound misogyny and nasty "humor" in this thread.
Another example, the nicknames on MTF are rude and mean-spirited: Piggy, Frauderer, Muggay, Fakervic, Nadull, Olderer, etc. Those are just too vitriolic to be fun.
In constrast, TF's nicknames are goofy and light-hearted. Most come from inside jokes or stories that make the board feel a sense of community: Martha, Chucky, Sarin, Vinas, Agatha, Cake, Medusah, etc.
The only MTF nickname I can think of that comes from a funny story is Pics. There are probably others though, but it's just not the same.