That is really a tough call.
I would say the clerkship would be the deciding factor in pushing me to say NYU/Boalt. They are very prestige driven jobs, I think the top 10 standing would help you. At the same time, top of your class at a top 25 has you standing out a fair deal as it is. You'd likely be a "shoe-in" at whatever local district court you are close to. A bit more questionable if you are hoping for Appellate. If you harbor any SCOTUS hoop dreams then I think the transfer option is no question.
I'm sure you will place well in the major California markets (San Fran, LA, San Diego) if you stay put. It's impossible to deny Boalt's placement in the elite Cali firms however. They are the big dog in the state.
Aside from that, I might say to stay put. I think you are the first person on here or the Yahoo board I have not recommend to transfer hands-down.
Best of luck to you either way. Congrats on an amazing 1L.