Wow! You live in CA?
It's a good thing that you understand the value of paying your mortgage down faster.
One question: Do you have an emergency fund? As in a good 6 months' of expenses in something liquid (like a money market, cash, etc.)? If not, you might consider building that up to something reasonable before adding payments toward your principal. You'll want the emergency fund there because it's a lot more difficult to pull money out of your house if you actually need it!
If you already have an emergency fund, I'd try to knock down the higher-rate payment first because you'll "earn" 6 5/8% (minus any lost tax deduction) in saved interest for the extra amount you put toward principal on that loan. Then, after the first loan is paid off, you can throw that whole payment at the bigger loan.