The big-firm model is highly VC-focused, though, and can be somewhat inflexible for bootstrapping types of ventures. It all depends on where your company is at.
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.
Still, if there's that prior relationship between the firm and some investors, how can we be sure our interests are being best represented?
We don't use them anymore, and I don't think there is much value added to justify the added cost of a large firm.
Do go with vanilla docs though.
Deferred costs is a fair deal. Of course, the bill will be large once you have to pay it, but at least it's deferred. Just make sure that it's truly deferred forever. If it's deferred for 6 months or funding (whichever comes first), it's a bad, bad, deal. Debt bankrupts companies.