I have a C330 that I used to shoot weddings with - almost exclusively with the prism finder and the left hand trigger grip.
I used to mount a Metz 60 CT flash-head to the grip as well - all together quite a large piece of kit
.
I also own and use a Mamiya 645 Pro with prism finder.
Here are a few observations:
1) The C330 (or C220) with prism is a fair bit dimmer than the 645 Pro with prism, but I still found the C330 with prism worked well for weddings;
2) Both the C330 (or C220) with prism and the 645 Pro with prism give you an image that is right side up and right side around;
3) Don't confuse the C series porro finder with the C series prism finder - the porro finder is large, quite dim, and images are laterally reversed. It is, however, quite a bit lighter than the prism finder;
4) The "native" orientation for the Mamiya 645 cameras I have used (the Super and the Pro) is horizontal. You have to turn them sideways for a vertical orientation;
5) I prefer the left hand grip for my 645 Pro to the right hand power winder, but I am left-handed.
Hope this helps.