Dough and cold fermentation

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I've produced four or five really tasty loaves this week. The first couple were from a batch of dough that I threw together, had at room temperature for around three hours, stuck in the fridge for 24, pulled out, warmed to take the chill off, shaped, proofed, and baked.

The second batch was dough I threw together, stuck it straight in the fridge for 48 hours, pulled out, warmed to slightly below room temp, shaped, proofed and baked.

The flavor of both was top-notch, the crust is crisp and has some great blistering. The crumb is pretty good for a ~65% hydration dough. I'm a little disappointed by the oven spring in the second batch, however. I also noticed that while the first batch crackled as it cooled, the second did not.

My question is: after the dough comes together, does one get better spring by first fermenting at room-temperature for a while before sticking it in the cooler? It doesn't quite make sense to me given that the dough gets knocked around during shaping and is given a chance to proof. I know I proofed longer the second time as well; perhaps I over did it? I find it difficult to determine when the proof has gone far enough, and so any tips would be appreciated.