I directly compared Sierra RAAL towers to F226Bes side-by-side many, many times across several musical genres and tracks in my primary room. While the Revels high-end is impressive, smooth, and detailed, the high-end on the Sierra towers is at worst just as good and at best significantly better. For well-recorded acoustic guitar, higher-frequency vocals, and the like, there's really no contest to my ears. The only time the Revel tweeters sounded better to me than the RAALs is when standing up or lying down outside of the vertical sweet spot of the ribbons. The Revels are great if you're in an environment where you're standing / walking around a lot while listening, like say in a game room. Due to their more limited vertical dispersion, the RAALs start dropping off quickly once you leave the sweet spot up or down; not so with the Be tweeters.
The LX tweeter I find is very close in tonality and overall sound signature to the Revel Be tweeter. While I've never compared the LXs and Revels side-by-side (they're in different rooms), I've never heard anything in the treble range of either one that made me think there would be any great distinction between them were I to do so. Both are excellent. Both take a back seat to the RAAL towers in this area.
On the other hand, the F226Bes offer a noticeably fuller and smoother midrange compared to the Sierra towers, as well as more slam and presence in mid-upper bass. This makes them a better and more versatile choice for harder rock / metal, large and powerful orchestral pieces, and similarly dynamic / complex material. The upcoming Klippel-revised versions of the Sierra towers will surely close this gap.