Just some general comments based upon having watched Ranger Tugs for a few years.
Comments apply to boats beyond the factory warranty period.
If there is a defect in the boat due to Ranger Tug/employees they cover it! I have not yet seen a factory defect which they do not make right.
So, if you buy a 4 year old boat and suddenly discover that plumbing was installed backwards, or bolts were left out of the engine mounts, or the wrong gauge wire was used and is now melting insulation, or the deck is falling off the hull, (or some such) my belief is that the factory will step up. That belief is based on the level of commitment I have observed in their dealings with customers owning second or third hand boats - including me.
Installed equipment comes from other companies. This is engine, tranny, thrusters, and on, and on. There you will have to speak directly with the company that made the parts. (this is the same for all boat makers)
Equipment can and does fail. Just normal use and wear will eventually fail 'all' equipment on the boat, someday. That is hardly a warranty issue.
Your level of satisfaction in dealing with these supplier companies over issues of failure or malfunction that you feel were due to a defective unit may not match that feeling of satisfaction you get from Ranger Tugs.
Life is a crap shoot. But in general with buying a used Tug you have better odds of being satisfied in the end than with any other boat maker that I am aware of - at least below the multi million dollar yacht range.