In my experience I do find that Bernal Heights usually tends to be sunnier than Sunnyside.
The summer is a perfect time to witness the fog rolling in most afternoons around Sunnyside and most areas to the west. As far as your investment goes, a good Realtor will certainly be happy to show you a history of home values in both neighborhoods. If you are not already working with a Realtor, give me a call and I will be happy to help you.
Patrick Lowell, Realtor, CRS
Zephyr Real Estate