See here

I can tell you 3 diff.:

1. S corp is pass through tax entity, S corp doesn't pay corp tax, all share holders pay income tax when they get money from S corp.

C corp needs to pay tax at corp level, but if you distribute majority of the profit to shareholders, you pay minimal tax on that c corp income.

2. S corp can't have foreign share holder, C corp can.

3. C corp can have better medical write off, if you know how to set up.

You can convert S corp to C corp later, when needed.

If you have plan to go after VC, you better have C corp.