Very much depends on the individual properties: I had consistently very nice upgrades to HUGE suites in Barcelona and Fort Lauderdale. Large standard suites/corner rooms in HK and NY Union Square. But absolutely no noticeable upgrades on multiple occasions in Mexico City, NY Midtown, Miami Beach despite being told I am being upgraded (I'd hate to think from what).
The Ws seem to have so many types of "suites" that anything can pass for an upgrade...