if a RT machine is cleaned every day, **thoroughly**, it shouldn't have any problems with scratches/rt marks...
I agree with you that rotary one-shot is the best for consistency, but some people
1. don't have the space for a processor(Jobo)
2. don't have the money for the chemicals to buy in enough bulk to bring cost down to a good minilab's price point
3. the convenience. If the lab keeps their chemicals fresh, and run daily(if not every 4-6 hrs) control strips, and keep their machine's clean, there shouldn't be any problems?
personally BOB, I'm still with you on using rotary for c-41/e-6. I've had some bad experiences with dip-n-dunk processors(bottom sheet is pushed from 1/3-1 full stop more than top of the rack sheet<first in, last out>)
but some people don't have the luxury of space for storing chemicals or a dedicated film processor.
while I'm not at school, I take my film to Costco, thankfully they have a big enough throughput of film to keep their chemicals fresh, and I haven't had any problems with RT/dryer/any other marks/embedded dust so far. They only process 35mm though, which sucks, cause I shoot mostly 120/220.
but to the OP, shoot a color checker chart, or a step wedge, or a scene where you can easily access(back yard, or local park), record your time shot, lens used, and rough location of where you shot from, shutter speeds, film, frame #, etc.....
shoot two rolls, EXACTLY THE SAME. if you have 2 cameras, this will be easier. shoot the same film, same emulsion #(same pro pack/bulk box)
send one to your local minilab, and one to your pro-lab(where you've been going up to until now). wait to get results back, and then compare/scan/print same frames from each roll, and see if there's any differences in color balance/density/contrast, etc.....
these factors are all controlled by how thorough the lab is in maintaining ACCURATE development/developer/overall chemical temperature, and times in each bath(developer mostly)
decide which results suit YOU best, and what YOU want to achieve STRAIGHT OUT of the film, before any tweaking/scanning adjustments.
then stick with that lab.
you might also want to ask your minilab how many rolls of film they process a day, to give you an estimate of throughput.
best of luck!