The E906 is a far better microphone than the E609. but not as good as the MD421-II. If you have £400 to spend, buy the 421. The position switch on the E906 is very useful, I have used this mic on a wide variety of electric guitar amps, brass instruments, woodwind instruments, snare drums and even a few acoustic guitars without issue.
My biggest problem is the mic clip, which feels cheap and likely to break, just like the 421's. Why a £200 mic has such a cheap clip, I don't know.