Personally I think 800dpi of difference isn't noticeable.
Not to mention every gaming mouse should come with dpi settings, so if the price isn't that much different (I'd say, you are mostly paying for the brand anyway*), you should get the higher dpi and find out which suits you better.
In the end it doesn't matter. You will get used to either setting after a day.
* - Got myself a 4k dpi mouse that glows like a freaking rainbow for ~25$ and the next one with nearly the same setting (though, it was 5k, I think) was priced 4 times that.