Just remember that under the Marriott terms and conditions, suites are explicitly included as an upgrade option for platinum-elite status guests. Technically, gold-elite guests aren't suppose to receive a suite. Now, granted many hotels will claim a suite isn't available, but I wouldn't hesitate to push back and, if necessary, read the terms to the manager if you really care about a suite. Unlike Starwood, there is no limitation on the category of suites that one can be upgraded into as a Marriott platinum.