When in doubt, C Corporation.
Every bit of advice I got about corporate structure was mealy-mouthed, noncommittal, and almost completely useless. Unless you have a very strong set of attorneys and can afford to pay them to get you out of messes, you want a C Corp (or, if you do have them, you probably still want a C Corp).
What they never tell you about an LLC is that:
a) LLC operating agreements are roll-your-own documents without widely established boilerplate examples. Imagine trying to write a somewhat complicated word processing program that needs to allow for numerous bells and whistles (multiple typefaces and fonts, footnotes, and multiple paper sizes), but not being able to compile it or test it (or modify it) until after somebody buys it. It isn’t enough that a few years later when someone does compile it and run it (with a newer version of the compiler), that it works flawlessly, but that it has to have every feature they want! Oh, it doesn’t? See you in court. You can afford your own personal legal counsel, right?
b) Many investors won’t touch companies with LLC structures (probably because of reason a). Most investors (if the round is big enough) will toss them aside for a C Corp formation (also because of reason a).
c) Your state (even if it isn’t Delaware) has default rules for things in a C corp that you would forget to include in an LLC operating agreement.
d) MicroSoft L.L.C., Google LLC, Facebook Ltd.? No? They all started as C Corps. Bonus points for naming a company you do want to emulate that started as an LLC.
The only real pro to having an LLC as a startup is the lack of requirement for documenting regular meetings, which is a pain and easy to overlook (but a major screw-up when you do overlook it) in a C corp. Your CFO should know how to do this properly and take care of it promptly or you need a different CFO.