Bread is a series of trade-offs, time for flavor. There are subtle differences in what happens in a starter (like a biga or a poolish) versus retarded fermentation, there's more enzyme and bacteria action going on in the latter, the longer it sits around the more it starts to develop sourdough-like characteristics. I don't think it would be wrong to say that sourdough is the ultimate in retarded fermentation, as it represents the longest point on the time-for-flavor scale.
Does it make a BIG difference? You'd probably have to run side-by-side tests to see if you can even tell which is which.
When I was testing the baguette recipes for Peter Reinhart's 'Artisan' book, I tried delayed fermentation periods of up to 7 days. (After about 7 days the dough got funky, 1 of 3 test batches had to be tossed out on day 6 because I no longer trusted it.)
After about 4 days, the dough and resulting bread took on characteristics similar to a sourdough, with a slight tang in the taste. I thought the bread was best after about 48 hours of retarded fermentation, my wife and son couldn't detect any significant differences. The dough felt different, though, and I think there were differences in the crust as well.
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