Ki Pro is a video recorder which works independently of a computer (though the format it records to is ready to edit for FCP). It's initial 'remit' is work with cameras. It cannot be used as a video output device for a computer. It is a Pro Res only device.
The IoHD is a video Io box that is tethered to a computer. It can capture with and output video from FCP and work with other software products. Whilst it can be configured to work with other codecs IoHDs main appeal is when working with Pro Res.
Both use hardware to encode Apples ProRes.
Both have hardware up/down/cross conversion (scaling) for input and output built in.
Does that help?
EMEA Business Management for AJA Video Systems Inc.