It only really matters if your 0-employee company is profitable.
If it is, then presumably it's a pass through for you, showing up on a 1099 or a K-1 maybe... In any event, the income is appearing on your Schedule C.
An individual 401k will let you take not only the standard deduction, but also a matching funds deduction since you are the equivalent of both employee & company. Net, you can contribute up to I think something like $50k (but you have to be pretty profitable - I'm going off memory here - like over $200k profitable); that's a lot of tax savings - potentially a great deal if you foresee less income in the future where you'll be contributing less to your retirement than you can now; these plans were created with the idea you'd usually contribute the same amount each year, something not too realistic for many who are self-employed.
If you're not profitable or not strongly profitable, then I think all the plans you listed are basically the same from a tax standpoint - you can tax-free contribute up to something around $18k.
Unless you really need the tax deduction for some other source of income, you might be better advised to put your retirement savings towards a Roth plan - it's theoretically at least a better deal for retirement. Really, it just depends on your goals here.
Most people in startups aren't operating on huge incomes, so saving for retirement is usually a question of discipline than tax efficiency.
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