I've lived in both places and can sum them up as such:
San Jose = Live to Work
San Diego = Work to Live
In San Diego, your nieghbor works for PG&E, has a cabinet business or is tech support for Qualcomm. In the Bay, your nieghbor manages terabit networks for Yahoo or owns his/her 2nd-3rd software company.
For just about all types of tech (semis, product development, Internet, Software, etc), the Bay Area is utopia. If you work here for a few years, you can pretty much go anywhere else in the US and become a big fish in a small pond. That's the real allure to the area, world class tech opportunities.
On the other hand, San Diego has some of the best weather on the planet.
The tradeoffs are yours to choose.
You will miss the beach if you move here from Socal. The coast is alot different up here and IMO, Santa Cruz is pretty forgetable. The traffic in the Bay Area is also much worse than SD.
If you need the beach, you will find yourself driving south to Monterey/Carmel/Sand City.
BUT.....the Bay Area has Tahoe....which is pretty unbelievable if you have never been there.
