At one time I owned both, but I sold the I3 many years ago. It was a good keyboard, but nothing compared to my S-950. The days of lugging two keyboards to a job have long since been over for me. One lightweight package is all that's needed for my jobs.
Gary

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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)