Are you fling a return for the 2019 calendar year? If so, you should be aware that either return would be considered late at this point (Form 1120-S, for an S corporation was due March 16th).
Further, Form 2553, the form used by an entity to elect to be treated as an S corporation, is also late (although there are late filing relief provisions).
See https://www.irs.gov/instructions/i2553#idm139773190567344
Further still, you might want to review the information available at the IRS site regarding S corporations (link below).
See https://www.irs.gov/businesses/small-businesses-self-employed/s-corporations
Finally, you should seek professional legal and tax guidance with respect to this decision. Basically, S corporations are pass-through entities (all of the income, deductions, credits, etc. are passed through to the shareholders) and, thus, are not taxed directly while C corporations are entirely not pass-though entities and, consequently, are taxed directly. The result, essentially, is that, as the sole shareholder of a C corporation, you could be confronted with double taxation (the corporation is taxed on its net income and then distributions from earnings and profits are generally taxed as dividends).
Again, consult, in-person, with tax and legal professionals.
