Bob,
Ron covered one part of your question for you, let me try to hit on the other part. I have always operated a small shop. I bought the 4366 press after considering all the options and here is why I settled on the larger press.
True, you don't always have extra large pieces to mount, I'd guess most are in the 32x40 or smaller range. But, when you DO need to mount a larger piece, the smaller press is useless and you will have to find someone to mount the larger piece for you. That may be as convenient as running down the block to the neighbor frameshop or it may mean taking the piece to another town to have it mounted. In my case, there was nobody else within a 30 mile radius of my shop that had a larger press so I opted for the 4366 over the smaller one. I never regretted the decision. In 16 years, I haven't had a single piece of drymounting that I couldn't do in that press.
If you have the money to spend and the room for a larger press, I would recommend buying the largest press you can afford. The size of mounting requirements may change as people become aware of your press and you may get more of the larger pieces in for mounting, as I did.
I have done many maps, architectural renderings, and visual proposals for some of my customers that I wouldn't have been able to do with little inconvenience on my part. The work I took in just from the cities around me for their road planning, zoning additions, and other city renderings kept them as regular customers of mine and allowed me to get their work done in a timely manner with a minimum of inconvenience for me.
Framerguy