Don't choose on RFP
Jeffrey Zeldman advices his fellow designers to never design on spec, concluding that "those who insist on getting free designs anyway are simply advertising the fact that they would not be good clients to work for."
Nor do they always do themselves a favor by choosing a designer on RFP.
I would say that, for the curious and open-minded, it is far better to surf the web and discover, among the lot of brilliant portfolios and creations, the ones that will strike a chord like no answer to an RFP ever will. Some consider enough to select musicians by requesting tapes, I much prefer to go to concerts.