We’re all different. I’ve been playing for over 30 years and use a 3. If I moved up to a 3.5 I would have a hard time and a 4, forget about it, couldn’t do it.
That theory of a stronger reed will give a better, smoother sound could be right, to a point…say when a student starts on a 1 and as they move up a few strengths. Not many people play 4’s and 5’s. For example, I’ve been a pro a long time and have many pro sax player buddies and none of them use these higher size reeds… the most popular tend to be 2.5, 3, and 3.5
But listening to what people say is not as important as what works best for you so experiment with the sizes you mentioned, who knows, you might be one of those rare types who will get along with a 4 reed. Try it, if it feels too hard and there’s no sound improvement than you you’ve found out for yourself. There’s other ways to get a better sound other than just moving up to a very strong reed size… besides breathing and long tone exercises I would also look at a different mouthpiece.
