You should write the story/plot you are enthusiastic about! The thing is, I think, unless you are disciplined you need to write about something you like to make it through every day. So if you don't feel good about your current story, maybe think of something new, or give it a few adjustments? But just because there's similar media shouldn't stop you if that's what you want to write.
(Though I have seen people wrote 50k in the first days, and ugh, jealous.)