Either of the above systems has strongly curved focal plane, Schmidt's very awkwardly accessible focus as an extra nuisance. How do you intend to deal with that ? Field flattener ? Film bending ? Schidt's fast f/ratio is quite unforgiving to focussing errors (some 50 microns for say F/2). Be aware of thermal effects - ordinary materials will expand/contract more than enough to defocus and ruin your photos completely. People used Invar rods before, I'd recommend using carbon fibre (for ANY photographic telescope, as a matter of fact).
Ritchey-Chretien is in my opinion far too complicated for amateur, without any real gains - it still has astigmatism, curvature of the field, and it's reall pain in the *** to figure.
Schmidt is really capable of excellent results, but again pain to use. Film cutting and fiddling with cuts is quite unpleasant experience (hypered Tech-pan id PHENOMENALLY sensitive to fingerprints !).
I'd personaly choose something with a flat, well corrected, easily accessible focal plane. I'd again prefer something that I can use with a "normal" SLR camera as well. Take a pick between Lurie-Houghton, Concentric Schmidt Cassegrain or Wright. CSC has the best performance, Wright is cheap, light and relatively easy to make, and L-H has all spherical surfaces.
8" f/4 systems comparison: Wright covers most of 35mm with 25 micron images, about 40 um in the corners Lurie covers 35mm with a bit better images (30um or so in the corners) CSC will cover large format (6x6 or 6x7) with less than 25um images
Good luck, Bratislav