IT'S FUNNY THAT YOU THOUGHT OF THIS!!
While I was in Tucson, I thought this exact same thing;
Rihanna releases a slow, melodic song with trancy elements (rude boy), then Chris Brown (makes his come back with and) releases "dueces", which also has a similar melodic production structure.
Next, Rihanna releases a fast, uptempo dance track WITH trancy elements (most pop artists don't use the trancy sound that blatantly today) then next thing you know, Chris Brown pops in with his second release being the one that also has a fast, uptempo dance track.
The only difference, though, is Chris Brown's track samples "i'm not alone" by Calvin Harris, and I'm not sure what Rihanna's track samples. I also can't prove that Rihanna's dance track was actually produced first, although hers was released before Chris Brown released his. There are also many other factors to consider - like the fact that he was struggling for a while to "get back into the scene", which may or may not have caused the "yeah 3x" record to not be released as early as it could have been... but all that is my own pure hypothesis and speculation. I also can't assume Rihanna "copied" since Rihanna has already proven that she does both dance and slower pop / r&b.
