I can't answer about Windward, but I can give....
you my expereince with some of the second line companies. We've chartered about 6 or 7 times over the past 15 years, twice with Sunsail, several times with local high-end companies and a couple of times with "discount" charter companies. In 1993 we chartered for six weeks with North/South in the BVI. Their rates were on the same scale of what you describe, about half the price of Moorings and Sunsail. We were on a 41 foot C&C which was barely OK, but considering what we saved, was probably reasonable. The boat was back to the charter base several times during our stay for repairs, including a never successful effort to install a working depth sounder, which at the time ultimately kept us from going down island - our original plan. We still had a great time, but not what we expected, and with quite a bit more aggravation than I would have liked. I've learned to ask carefully about the age, condition, accessories, etc., of the boats I was going to be chartering, if there were off-limits areas for them, and how far their support extended. This past March we chartered for a week through Sunsail in Antigua, and their support was phenominal, and condition of the boat was great. Their base operation was top notch. We've also chartered with small local companies (in Maine and the San Juan's for example) which gave great service, but at not-killer rates. Hopefully someone here will have personal experience with Windward.