Caliper Signature vs Duetta Signature?

Hi guys,

Just a quick question regarding the difference between these two Apogee models.

I know that a lot of folks regard the Duetta Signatures as the next best thing to a pair of Divas, but I'm having a hard time determining the difference between the Duetta and Caliper.

Is the Duetta bigger?

What is a reasonable price for a pair of Calipers in excellent condition?

Thanks for your help!