It's just as easy to convert an LLC to a C-Corp unless you've done something really crazy in structuring it. Google the advantages that an LLC has over an S-Corp and see how it all applies to your situation. Examine the differences regarding taxes, fringe benefits, RULPA, etc.
For most use cases, I strongly prefer an LLC to an S-Corp. The S-Corp is basically dead as an entity for new ventures, because most if not all of its benefits have been surpassed by the LLC.
Since I'm not big on 'flipping' companies, I even prefer LLCs to C-Corps USUALLY. I have also received VC funding for LLC startups multiple times, despite reading that it is 'basically impossible' in numerous articles. It IS more difficult to get funding as an LLC in most cases, but in some situations it is actually easier to get outside investment as an LLC. [I received investments from two international firms (Irish and Chinese) and they specifically stated that they appreciated that we were an LLC instead of an S or C Corp! There are fewer restrictions on foreign investment and ownership in LLCs. We took the investment largely to get access to their distribution networks, and the flexibility of the LLC helped us immensely because you can separate 'ownership' interests from 'economic benefit' interests, etc. I also know some angel investment groups that prefer LLCs because of their flexibility.]
I've discovered that (well-intentioned) people often dispense bits of startup advice like they are undisputed truths, when they are actually speaking to their own specific history and goals. They will tell you that you MUST incorporate as a C-Corp in Delaware, for example. That may be a MUST for them, but not for you. Not every business wants to flip to Google or Yahoo within a year. Not every business wants to go public. I can't think of very many 'Universal Truths" about startups...you just have to research everything and make your own decision based on YOUR particular circumstances.