ralstar

A) not vulnerable 4♠ is absolutely correct bid. Reasoning: opener has 5+ ♥opponent responded with 4+ ♥ partner has 4+ ♠and you have 3[spades. With opponents with so many hearts they are pretty much guaranteed to make 4♥. Conversely you have chance if partner has 6+ ♠ at making 4♠. Additionally, most likely to be set -2 for -100, while not allowing opponents 4♥for 400 points. B) both vulnerable. 4♠would be a total sacrifice as only a slight chance of making. Also, you can hope opponents try for small slam and set, but still just gambling. With both vulnerable, it comes down to how aggressive you want to play. Me personally, 4♠every time and forget the consequences.