Mamiya c330, relative value of accessories

I have a number of Mamiya C330s and am planning on selling a couple of them.
But I don't know how to evaluate the relative value of some of teh
accessories. I have both a prism finder and a "sports finder" that looks
like the prism but uses mirrors instead of a big hunk of glass. Which one
of these is considered to be the more desirable? Or perhaps the more
valuable? I'm inclined to sell the prism just because it is heavier.

Thaks in advance for any advice.

Matt
www.traskphoto.com