I work for a dealership in Texas, the largest CAT dealer in the U.S. Our Ag division is very small compared to some of the CAT dealers though. With any CAT dealer you have one big store centrally located to the customers. They combat that with drop boxes in neighboring towns, so customers don't have to travel back and forth to get their parts. For my ag customers in my territory, we have offered to put a parts bin on their place that holds all the major components that we see the most common failures. We do on occasion have an oddball part that fails, but when that happens, if we don't have it in stock, we typically have the part within 24 hours. Some CAT dealers participate in a loaner program for the loyal customers. When your combine breaks down and we can't get it back up and running within 48 hours, we will loan you another machine to use so you aren't losing valuable harvesting time. Like I say we are small fries compared to the guys from Bulter, Ziegler and Altorfer and this is a handful of things we do for our customers. I can't speak for the competitors, but they do have an advantage on us, because there are more of them per square mile. We try to make up for that by having these expensive trucks that we can keep weirdo tools in that our mechanics might need at some point. A CAT dealer can typically do the things in the field, that your Deere or Case dealer has to bring to their shop. Less hassle for the customer.
Our combine compared to the competition. There is no comparison in corn. Our combine will outperform anything out there, class for class. Then of course we have the largest combine in the world. Soybeans, from what I have seen is one of the tougher crops for our combine unless you spray them first. It will still run with anything out there, but it won't leave the competition in the dust like it will in corn. Wheat, pretty dang productive. As far as clean sample.... how clean do you want it? It's about as clean a sample as you can get from a combine. It will take you a little use to getting the setting right for your conditions. Quite honestly the settings from the factory might not even get you close at times, but it is a decent generalization of where you should start.
Hope this helps.
Jason