Because the nature of Ravenclaw House is more light-hearted or studious, as opposed to the valiant Gryffindor or the the steadfast Hufflepuff, it's not surprising that a number of Ravenclaw students would avoid fighting for either side. A major saying in Ravenclaw is "Wit Beyond Measure Is Man's Greatest Treasure", meaning the ability to think on your feet, and come up with something new and inventive on the fly is more important than political power or chasing down a lion. To say that Ravenclaw is the "grey" house is a misstatement, since it is Hufflepuff that exclaimed "We'll take the lot" when chosing her students. And that is not a bad thing. It is a show of acceptance and an understanding that everyone has value, even if they don't always see it themselves. So, why are Ravenclaws so boring in the Harry Potter book series? Simple. We don't spend enough time with them. More on reddit.com

I guess creativity More on reddit.com

Gryffindors are hotheaded I reckon. They're brave, but can often act without thinking. Harry is the prime example, and although Hermione is the opposite, she was very nearly a Ravenclaw. Hufflepuff I think could be too nice? Selflessness is great, but self preservation is also pretty important. In the Sorting Hat's songs it sad Hufflepuff "took the rest". So their flaws could be anything, because there's so many different types of people. Ravenclaw are obviously the clever lot, but they can be pretty arrogant if I recall correctly. Because intelligence is highly valued by almost everybody, they think themselves superior. More on reddit.com

I'd say for Hufflepuff that loyalty is not always a good thing. More on reddit.com