I've had both and they both have their strong points. Midjay has vocal processor, if that's important to you, but the vocal harmonizer is strictly a vocoder.
Also, you need an external screen with the BK7m if you want to display lyrics from text or midifile.
I'm waiting to have a look at the Midjay Pro that is just being released.
BK7m is much less expensive.
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DonM