I can't disagree that Moreno has (had?) more of an edge but I think that's what was called for in most of the "spitfire" roles (of various ethnicities) in which she was cast and trapped before and including West Side Story. However, though it wasn't a lead, her Tuptim in The King and I was certainly more of a standard sweet ingenue and it didn't seem to strain credulity getting to that performance. In 1961 (same year as WSS) she also played Rosa in the film of Summer and Smoke, which, if memory serves, was somewhat more restrained.
And personally, I would have enjoyed seeing a BBB Rosie with some edge.
Looking at her Imdb credits, I'm a little shocked to see that her Oscar win didn't lead to another role in a feature film until Popi in 1969 (8 years later) in which she played Lupe.....a Latina spitfire.