Lawyers and investors aren't particularly tightly linked in Silicon Valley, so I wouldn't consider their investor community in making a decision about using them. Besides, if the investor were tightly linked to the lawyer, you couldn't count on the lawyer to represent your best interests in a financing with that investor.

Larry Sonsini can help you meet investors, but if you can get Sonsini to represent you, you're probably already past the hurdle of meeting investors. Look instead at the quality of their work and what they will cost you.