The questions you need to ask yourself are:
- Do I need +1 AND +2 octaves up, like on the full-size POG?
- Do I need detuned octaves and a low-pass filter for extra creative flexibility, like on the full-size POG?
- Do I need full-fledged "organ" sounds, more full and convincing than what's on the Micro POG?
- Do I have space to fit the full-size POG on my board?
- Am I willing to deal with the 18VDC wall wart of the full-size POG, or is the 9VDC Micro POG the better choice?
The full-size POG is not only full of extra features, but also extra inconveniences. The Micro POG is far smaller and more convenient, but is pretty much a stripped-down version of its bigger brother.
Time to start interrogating yourself.
