Don't get blue switches. They suck at fast multiple key taps (details below). Amazing for typing though. I strongly recommend red keys.
The way the switch works on blue switches is the click point is below the reset point, and it takes a split second longer for the key to come all the way back up past the click point (not noticeable really while typing). What tends to happen then is the key seems to be all the way up when you double tap it, but the second tap won't register even when you feel the click (or you won't even get the click if you tap very fast).
What does this mean for typing? No real down side, and the click is good for typing rythm IMO.
What does this mean for Osu!? Any time you get a lot of fast tapping (so most maps above a 2* rating) there's the chance your fast repeated key strokes won't register, or the key won't pass the click point before you need to tap it again. The faster the beatmap, the more this will be noticeable.
With Red switches as far as I know the reset point is a bit lower, without the delay of resetting a clicker, so it's a lot better for rapid key mashing (like Osu!) where every tap matters. Black switches are even better because the harder springs cause the key to rise faster, but then it take more effort to push down, causing tired fingers after longer sessions. If I remember correctly on Brown switches the reset point is below the clicker, so it doesn't have the double tap issue, while still having tactile (but less audible) feedback.
This is why on many reviews/explanations of cherry switches you'll see they refer to Blues as the best for typing but not for gaming a lot of the time. I always forget what was special about Greens but many people recommend them along with browns for typing/gaming mixture (a quick google on Cherry Switch types should bring up a page with gif animations and explanations on how the switches differ, along with force required to press, time to reset and other details)