Why does rendering on a PC take 10 seconds compared to 0.25 seconds in-camera?

Thanks sjprg.

It seems your experience with the MPB 17” speed is similar to mine (although I cannot see exactly the specs of the specific machine you refer to). Also, the NR I have selected perhaps makes the process at my side a bit slower.

The i7 920 you refer to, is that a Windows machine or a Mac? If it's a Windows machine, then your mail suggest that the Windows version of LR would be (much) faster than the Mac version, using similar processors - something your HP laptop experience seems to underline. If your i7 920 is an (i)Mac, then it really seems to depend on which Mac you use.

I am considering to buy an MBP Retina 15” with an 2,7-GHz i7 3820QM processor and 16 GB of memory. This would replace my mid2010 MBP17 with 2.66-GHz 620M. So its going from two cores to four cores, and from a Geekbench score of 5,423 to 12,225. Just wondering how much rendering speeds would benefit from this investment.