> Is there anything I am missing?

Like, lots, I think.

I don't own property in Switzerland, but you write as if property transactions are in cash up-front. Instead, you put some money down (why the GP mentioned leverage), and the amount you don't make back by investing in stocks is this opportunity cost. The amount saved in rent is also subject to compound interest; unless you are worried that this person is a serial home purchaser those savings will be invested in the market.

I'm sure you can come up with more details and that the market probably wins, but you asked what you were missing.