What should designers consider when starting their business (LLC, S-Corp, and Partnership?)

At the risk of being evasive, there are a multitude of factors which go into the form of the business entity which you might ultimately decide to incorporate, including the number of members/shareholders and managers/officers, the structure and corporate governance, the liability protections which you are seeking and management style.  You should meet with an attorney and an accountant to discuss all of these factors before incorporating your entity.