Something you'd never get on a Yamaha board (unless a genos or Montage maybe) much, much less a stage board but the SKpro has the following waveforms:

I counted 5 trumpet & T-bone falls, gliss up, etc. in several variations.

13 percussion combos and/or variations to sync with your organ.

Pedal steel, choir and other ethnic stuff.

Having now been able to spend some time on the SK Pro, I'd sum up the major differences this way (where the first 6 advantages for each are kind of related to each other, before diverging):

YC61 advantages
* FM generated sounds (in addition to the sampled and modeled organ sounds)
* real-time effects controls
* smooth sound switching BETWEEN Live Sets (though limited WITHIN a live set)
* audio over USB
* 4 MIDI zones vs. 3
* interface generally easier to use
* LED drawbar indicators (vs. screen display)
* LED ring endless encoders for knobs that are always in the "right" place and indicating their current setting
* about 5 lbs lighter
* $500 cheaper
(also available in hammer action 73 and 88)

SK Pro 61 advantages
* VA mono synth sounds (in addition to the sampled and modeled organ sounds)
* real-time mono synth controls
* smooth sound switching WITHIN a combination (though limited BETWEEN combinations)
* volume control for its external input
* more internal split/layer flexibility (4 part vs. 3 part; and a single part can have up to 4 sub-sounds)
* deep sound editing
* assignable outs
* larger sound set
(also available in 73 key waterfall)

There are lots of other more subtle differences, but those struck me as the more obvious ones.

In sound, I think most would agree, Hammond is stronger on organ (esp the Leslie sim), Yamaha is stronger on pianos. Other acoustic instrument sounds could go either way, depending on which sounds you're comparing and/or personal preferences.

Action is also subjective, I think the YC61 is better feeling overall, though Hammond has the organ-specific advantages of high trigger point and simulated multi-contact triggering.

In the end, despite the talk by the OP of the advantages of the SK Pro (and it IS a nice board), I don't see it as a blow-out by any means, they each have some significant advantages that could matter more to someone.

I am encouraged about the possibility of some significant enhancements to the YC61, since ideascale has recently shown a whole lot of ideas moved into the "assessment" or "refine" category, which tells us they are actually looking into those possibilities. How many of those things they implement, and how well, and how soon, is all unknown... but it is at least an indication that something is in progress in terms of an update.