I'm planning a US road trip and want to stay at Marriott properties. I'm planning to be play it by ear a bit and be flexible with where I end up each night, and might not know where I'm stopping until a few hours before I show up at the property. Booking that close in, I'm wondering if folks think it's best to make reservations through the website/app, or if I should call the property directly?

I'd prefer to book using the website so I can use certs for some of the nights. But I'm worried that there's a lag in the system where either the online inventory doesn't match the actual property's inventory, or that the online reservation won't show up right away at the property. (Usually I make my bookings well in advance via the website/app and have never actually made a same-day reservation.)