Even if you are not legally required to register for VAT, you may want to do so anyway. Depending on your market, suppliers who aren't register for VAT may be perceived as less legitimate. Also, if you expect to grow your business and exceed the compulsory VAT registration threshold in the future, then it may be easier familiarising yourself with VAT administration now instead of trying to figure all of it out at the last minute with SARS breathing down your neck.
Agree with Greig on the perception of a supplier who IS registered for VAT.
However, don't waste your time trying to register with SARS until you have at least R50k of turnover invoiced out and movement on your bank statements. They require R50k turnover as a minimum before they will register your PTY for VAT (not sure if this has changed with single reg, but was the case till recently given the high rate of VAT fraud in SA).
So, reg company, get trading, get to R50k of invoiced turnover, then weigh up pros and cons of whether VAT is worth it for your particular business and client base and make your move.