It's a pretty cheap toy if nothing else. I assume that since it has midi in and out, that a midi controller could be used if the small keys are a problem. I couldn't find any detailed midi data in the specs.
You ‘ll have the following pros.
1.10 lbs pro arranger KB with speakers and aux input (buy your 199$ TC harmonizer and hook it up)
2. Actual midi ports and L/R out, sustain and assignable ins
3. Plays SMFs or Modified SMFs with internal sounds directly from SD with no load time
4. Good synth engine/sounds and tons of editing (will load Triton programs)/Actual sequencer with true edit
5. Can rewrite all factory styles (4 variations each more than 300) and user area (can load 48 I believe), but you have SD drive –so no major issues
6. No sticking USB drives
7. arranger module with 5 octave keys (I know the size) with 4 WAY JOY STICK ( try that with PSR s 650) ( did I mention speakers and 10 lbs only?) meaning you can create , edit songs anywhere without a computer or space issues.
Cons will be
1. 2 fills and some issues with fills (same old PA 80 BOARD)
2. Muti-pads won’t play loops (no OS update can’t do it either)
3. Styles somewhat busy and over orchestrated compared to mid Yammies ( PSR S series)
4. Small keys ( I would still take the keys than no keys at all)
The same functions /sound board as PA50SD , so you can check the manual.
http://www.korgpa.com/en/support/products/arrangers/pa50sd/pa50sd-manuals.html