I apologize for not being very clear in the prompt, there's no set definition for genderbend and genderswitch that I know off. I probably should just have said girl!Tsuna.^^;;
I normally use genderbend as a general "character in the opposite sex from canon" meaning, and genderswitch as a "character gets somehow changed to the other sex". In this case, I meant that a suddenly-girl-because-of-weird bullet/bazooka/whatever!Tsuna or a born-girl!Tsuna were both fine.