Audya is much easier. The Operating System is much improved.
However, if I were doing 95% midi files, I would certainly use a Midjay and save a few thousand dollars. You can midi a light-weight controller to it and have arranger functions as well.
Main drawback of the Midjay is the Vocal Harmonizer. It's not up to par with the SD1, and WAY behind the Audya. However, I just used a TC Helicon unit I bought for $300., and was quite pleased with the Midjay.
DonM