Both are excellent knives and offer top notch fit and finish. There are really only five differences worth noting.
The two obvious ones are the difference in overall shape of the handle and blade. I prefer the handle shape of the Stretch, as it fits my hand perfectly and positions it very reliably. I'd have to give "style points" to the Caly 3 blade shape, but the narrower blade of the Stretch does give it the advantage for deep cuts that need to curve - like cutting a plug out of a watermelon. I also find the Stretch II's edge shape, with its longer straight section and curved tip, more versatile that the almost totally curved edge of the Caly 3.
The third is the blade steel, Caly 3 is laminated ZDP and the Stretch II is solid ZDP. So, Stretch II will scratch less, but develop more of a patina if used to cut certain foods. I'll take patina over scratches any day, but you may feel otherwise.
Then theres the finish on the CF - smooth matte on the Caly 3, lightly textured on the Stretch. Again, a matter of taste, but I like the added traction the texturing provides. It is much less agressive than the texturing on the CF Military, which I find way too rough.
The final difference is size. Caly 3 is 4 /1/6" closed with a 3" blade while the Stretch II is a bit bigger at 4 7/16 closed with a 3.5" blade.
If nothing it the above pushes you firmly one way or the other then "just buy both".

As for me, I own them both, like them both, carry the Stretch II a lot more often.
Paul
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