I have the Copper Johns standard, pro, and the Spot-Hogg Bare bones on three different bows. The outer diameter of the pin guards seem to be the same, but the Spot-Hogg is much thicker, so you don't get the same open view you get with the Copper Johns. Also the Copper Johns mounting bracket places the sight further from the riser - and advantage if you have a fast bow. The Spot Hogg mount hugs the riser more and is an advantage in protecting the sight from random bangs. I prefer the close in mounting, but dislike the white ring that Spot Hogg uses to outline their sight window. White reflects light too much, and does not seem to be the sensible choice to use here, the orange of the Copper John is better.

I haven't detected any difference in noise between them, although the position of the Copper John away from the riser might encourage resonances. Copper Johns has sent me (gratis) some of their old model
mounting plates which will pull the sight in closer, but I haven't had a chance to use them. (The Copper Johns are not unusually exposed, it is just that the Spot Hogg is definitely more pulled in than most sights.)

I prefer the sight picture through the Copper Johns, but not enough to ditch the Spot Hogg on one of my bows. I use only one pin; perhaps that has an effect on my inability to detect any "resonance". Finally, I like the look of the Copper Johns Pro model over the standard model - a bit more streamlined.