I'm in the "I don't care" camp primarily. However, I do have to add a note about MTF genderbenders. If there is any smut of the "hard-core" variety at all, smut + MTF gender bender are the single worst combination in existence. I absolutely loathe it with great intensity.
MTF genderbenders that actually explore male and female roles in a non-sexual way, or if they cross into some soft stuff (max threshold is the level that Ranma 1/2 went to) for the purpose of facilitating this exploration of the gender roles, then it can actually be VERY very good. But, way too many writers these days tend to just do it for the smut, and that's gag inducing. I don't want to read about your auto-gynophilia fetish.
Even if you don't want to explore gender roles, just don't put smut in there. It can still be good if you just want a female character but you say they were a male in their previous life.
As for FTM genderbenders, well... those are always bad. Smut or gender-role exploration, they always turn out bad. I think the main reason for this is that our society really is very in touch with what male gender roles actually are. There has been a lot of exploration about female gender roles, but whenever someone SAYS they want to "explore" male gender-roles, it always winds up heavily steeped in feminist propaganda messages of male-bashing of the worst kind. Interestingly, there's much better exploration of male gender-roles in MTF genderbender stories. I've not really seen any FTM genderbender stories other than pure 100% smut, but even then it makes me cringe to think about what would be done outside of it.
I guess it could be interesting if someone actually was quite honest with the exploration of male gender roles, but even if that was done I don't see it being very successful. A very honest FTM genderbender story would likely just look no different from a teen male coming-of-age story.
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EDIT: Actually, that's an interesting hypothesis on male Vs. female gender roles and why they are and are not interesting in writing. If you think about it from the coming-of-age angle, if you think about the teen years of either gender, female coming-of-age has a lot of turbulent emotions, and male coming-of-age has a lot to do with learning how to treat girls right and navigating around the turbulent emotions of girls. In other words, the girls are the center of the story. When it's viewed that way, it really is no wonder the exploration of gender roles is always more compelling from the female perspective.
Of course, that's just my thoughts on the matter. People are free to disagree and offer an alternative hypothesis.