Squeak,
One of the differences of the QY boxes and the EX5 keyboard is that you can trigger the patterns on the QY just like an arranger keyboard as long as you use the 3 finger chord method. The QY will not recognize single finger mode. You can also use it just like the EX5 sequencer as you mention using the 8 track pattern sequences along with the 16 track linear sequencer.
The major difference between the QY70 and QY100 is that the 100 has a smart media slot for storing and loading midi files and there is a seperate effects unit inside the 100 for use with a mic or guitar. Other differences are being able to use a sustain pedal on the 100 for start/stop and other functions.
The QY's run on batteries or A/C and are quite small and are great for use as a midi sequencer, tone module and arranger when used with a digital piano, lap top, etc.
George Kaye
Kaye's Music Scene
Reseda, California