Hmm, i don't see nothing unusual in the stats, but i noticed that your scene in old screenshot is set at 5,0% noise target and in the new one, it is set at 4,5% Not sure if that alone can explain estimated difference, but i think it would be better if you'd set noise target exactly the same and let it render until it's finished. Estimated time is not necessary very precise measurement, especially after few passes, when image is still very noisy. One more important thing - does your old image was rendered in the same version of Corona? Noise calculation between different versions can vary quite a lot and that may give you different estimates and rendering times.