Yes, cost and packaging concerns do come up in the real world. That's why I mentioned them specifically earlier. The thing is, for both of the marques mentioned cost and packaging should not be a problem. If you have a longitudinally mounted inline six, or better yet a rear-mounted engine, you've got plenty of room for a double wishbone (or multi-link) suspension. Cost shouldn't be a factor either. If Honda could put a double-wishbone suspension in a $14,000 Civic more than 20 years ago, it shouldn't be too expensive for Porsche's $60,000 Boxster today.
Personally, I'd prefer a bicycle to any car with McSuspension if that car has a big price tag or any kind of sporting pretensions.
Of course, a SLA suspension is never a guarantee that the car will handle well. What is indisputable, though, is that a well-engineered double wishbone suspension is always going to be better than even a well-engineered McSuspension if all other variables remain the same.