ST6001 vs. ST4000 auto pilot
D, you seem to be focusing on multiple issues: resale, maintenance/repair and - presumably - suitability. And the two units you are considering are a bit apples vs. oranges. Here''s my take on what you''re choosing between:
6001: much quicker as well as more powerful; will handle your boat in virtually all conditions, and under power and sail; more expensive; electrically more thirsty; installation potentially affects use of space; stable product; independent steering system should you loose an idler, sheave, wire, chain link, etc.
4001: easy to self-install; excellent value; stable product; slower and less powerful, so boat can demand more from it than it can provide, e.g. in tough conditions or spinnaker in soft winds; electrically efficient; relies on existing steering system, so offers no redundancy
Of course, you''ve left off the information that would allow for a recommendation: how you use your boat? Not knowing how often, where and in what kind of conditions you sail, it''s impossible to know if the 4001 would be a ''best value'' choice for you, or would be hopelessly inappropriate. However, there''s no doubt about it: a C36 with a 6001 would be preferred by any potential buyer who knew much about a/p''s.