I prefer the San Diego since that is what I am using. Have you already used the CPU comparison chart that THG offers. If not that is a great place to start. I believe the SD chip is cheaper than Claw chip at Newegg.
the 4k san diego core is the better one. Less heat generated on a 90nm process instead of I think 113 process. ANd the san diego has the sse3 instruction set the clawhammer does not!
San diego has the E3 enhancements. SEE3 instructions, 90nm process (better overclocking), lower heat, better memory controller, and it is cheaper. Hands down, clawhammer should not be your choice, it has no major advantages.