You as an initial member can sell membership interest, but reselling that interest can be difficult or impossible for a VC. They're looking for future liquidity, and an LLC interest just doesn't have the same statutory guarantees that a C corp share has.
That's not really true either. If the operating agreement permits reselling then you can resell. A C corp's operating agreement can also restrict selling to the point that it becomes impossible - if that's what's wanted. It's common for investors to want such restrictions because they don't want to find that the other investors in the business have changed without their agreement, or that one of the founders has sold a share to an investor that they don't approve of.
And you can always go from LLC to C if you're taking VC investment.
And you should be able to stay as an LLC if VCs would learn to use blocker corps like PE shops do. VCs don't do that but not for any principled reason as far as I can tell.
This is not true. You can sell membership interest in an LLC the same way you can sell stock in a C corp.
And in my experience it's fairly simple to go LLC to C. I didn't get confused with S corps.