This is an excellent post. I agree so much that the best cruise experiences are the ones on smaller, itinerary oriented, casual ships. I adore Renaissance and Windstar for these reasons.
You put the two lines in perfect perspective, the service on Windstar (and food) is exemplary, and by the same token Renaissance is also good but they offer a similar product at a lower cost. Don't overlook the alternative dining options on Renaissance however, they are a big plus.
This brings to light the concept that perhaps bigger is NOT better. All the large cruise lines are building bigger and bigger ships so the overall experience is bigger, but the personal experience aspects of cruising -- getting to know the staff, getting personalized attention, feeling uncrowded and relaxed... have all gone by the wayside.
I can draw a parallel between small cruise lines: its like visiting an old friend; and larger cruise lines: like a trip to Disneyland. The first will leave you feeling warm and fuzzy, and the second will leave you feeling spent and exhausted. Both are interesting experiences, but I suspect you are more inclined to return to see old friends than you are to go to Disneyland year after year.