The differences will be in the length based on model year. The length varied by year. They all have fiberglass flooring, snap-in carpet, etc. Some years the bimini was standard, sometimes, not. The length of the swim pltform could be slightly large/smaller. Build construction is not substaintially different.
Some years the 230 was what is today's 240, etc.
I recommend you go to the four winns website and you can check out the previous model's specs. They have the specs and catalogs available online:
http://www.fourwinns.com/service/past_product