Wanted to chime in with our anedoctal feelings of how often we get suite upgrades for Marriott hotels after ~200 nights in KL over a 5/6 year period and 5-10 separate stays in each hotel:
Le Méridien KL - NEVER (only once with SNA)
Westin - seldom (10% chance)
Sheraton - seldom (10% chance)
JW - very high chance (70% chance especially for 1/2N stays)
These hotels only stayed once so more trips are needed for better data:
Renaissance - upgraded with SNA
St Regis - upgraded to suite without SNA
Fairfield Chow Kit - offered suite upgrade but declined due to mattress run