I'm at 40 SPG stays so far this year and most of the time I get a suite. A couple of hotels, like the Sheraton FRA and Sheraton CDG, never give me a suite. But the Sheraton AMS and every LM I have stayed at give me a suite every time.

Sheraton Delfina, never a suite. Sheraton Belgravia, always a suite.

Westin Dublin, always a huge suite. Sheraton LHR, never a suite.

Sheraton Park Lane, always a suite. Great Wall Sheraton, never a suite.

So I generally choose the hotels that offer the best overall experience and thus more often than not I get a suite.