Many, many years ago I went out with a group of people on a Columbia Contender - The company that later became Columbia had built the Islander Bahama for Islander, and the Contender was basically a rip off of it. Anyway, one of the people on board had a Magregor Venture (I don't know if it was the 21 or the 24) and said that the Columbia was a much better boat. I'd assume that the same would hold true for the Islander Bahama.
There are many boats in that size range on the market. You can get a boat in good condition for alot less then buying a beater and fixing it up.