What is the difference between a poolish and a biga? Both poolish and biga are pre-ferments. Poolish is a French name, biga an Italian term. What other differences are there between the two?

Just to give some direction: are there differences in making them? Can you both keep them as long? How does the dough feel with it? What difference does it make in the end result? Is there a difference in flavour/colour/texture?
I had to consult my copy of Bread Baker's Apprentice by Peter Reinhart to be sure, but here is a quote:


  There are two types of firm, or dry, pre-ferments and two types of wet
  pre-ferments. The firm pre-ferments are known as pâte fermentée and
  biga. The wet pre-ferments are called poolish and levain levure.
  
  ...
  
  Biga, an italian style of firm pre-ferment, differs from pâte
  fermentée in that it doesn't have any salt in it. Also, rather than
  cutting off a piece of finished bread dough to hold back as an
  improver, a biga is made specifically to be used as a pre-ferment.


So, it seems the main difference lies in the hydration of the dough, where a poolish is made with a ratio of equal water and flour.  There also seems to be a few other differences. A biga apparently uses .5 percent yeast to flour, while a poolish uses .25 percent.

Mr Reinhart does not say anything about a concrete difference in final result between these methods - just that a 'wet' pre-ferment is faster. Faster in the sense that in the same time-frame a poolish will develop more flavor and character than a dry pre-ferment.

Sadly I've personally only used a wet pre-ferment, since it is easier to handle. Just whisk it prior to bed time with a wire whisk and mix in the rest of the ingredients the next day. Having a full blown dough makes it more difficult to incorporate the rest of the ingredients.