I baked up two loaves this last weekend, the first with a two hour pre-ferment at 200% hydration and the second the overnight poolish. Last night I sampled what was left of both loaves and not only did the poolish loaf have more depth of flavor but the crumb was much more desirable. The first loaf, although good, was somewhat dense compared to the second one which had a nice balance of "big holes" and "small holes".