I enjoy K-On! a lot and it's been hard to find something to replace it with now that I've finished most of it. Honestly between the manga and the anime, if I had to choose, I would pick the anime. You aren't going to miss out on anything if you decide to skip the manga in favor of the show, because the anime adds more depth to the characters and a ton of anime original content that can't be seen in the manga. Who I do recommend this to is someone that has been through the K-On! series and wants to see more of their favorite charactersagain in a different medium. If you finished the anime already moving on to the K-On! College manga will provide you a continuation if you so desire it.