Back to the original question:
Weather: Cape Town's SE blows as regularly as Dr Freo, but is usually stronger, and often gets too strong in the afternoons, as in 3.5m2 sail in survival mode. I'd say - parity with WA on this point.
Water: Freezing cold in the Atlantic, except for the toxic freestyle pond next to the refinery (Zandvlei), and the secret flatwater spot South of Langebaan. Warm everywhere in WA. Waves are actually very inconsistent in CT, despite what the recent Fanatic/Swedish/German/Dutch videos would make you believe. Advantage to WA here (but not quite Perth).
Financial Considerations: CT is cheaper to visit and live in, but so is your life there. I'd say, parity with WA, considering the risks.
For me personally, WA is the place to be, despite some sensitive locals

.