Here in the UK we have virtually no SPG hotels but I would be very reluctant to book my biz stays with a 24 hour cancellation policy, since my schedule can change at the whims of others (no arguing with judges!). I probably cancel about 1 in 5 of my bookings on the day, and more than once have been advised of cancellation en route, one call to marriott and cancelled easily, without penalty or problem. It's a very significant advantage they share with IHG which is why all my biz stays are with these 2 chains.