To me the only ship I ever wanted was the Enterprise D, but I can tell you one thing, buy them for your own enjoyment, because they don't retain their value.
Well, I've seen some Micro Machine and Johnny Lightning models on eBay go for a lot more than the initial retail price, but yeah, buying collectibles on the hope that it will someday go up in value is probably not the best investment.
Eaglemoss did give us a wonderful Enterprise-D, though.