i posted response this in a similar thread a couple weeks ago;
I had the same questions about sunpower vs. powermodule - here is what reefgeek (ati's US distributor) had to say in an email to me;
The differences between the SunPower and the Powermodule are:
1. Housing Design – The housing design of the PM is a little bit more “SLEEK†and rounded. While on the SP, the design has more lines. But please note that the manufacturing material is still the same. Both are constructed of high quality aluminum.
2. Number of Fans – The SP’s have less fans, however this does not affect the overall performance of the SP vs the PM. The special design of the PM requires it to have more fans. While the SP’s design requires it to have less fans.
3. Reflectors – PM reflectors have a more rounded shape while the SP reflectors have a bent shape. Again, there is minimal performance difference between the two reflectors. Each reflector is still made of the same silver coated 98 PERCENT; reflective German-made Aluminum.
Overall Vincent, WITH the differences above, the PM performs only less than 5 PERCENT; better than the SP