ELI5: What’s the Difference Between Spur and Helical Gears?

I always wondered about the actual difference explained simply between spur and helical gears. The ELI5 answers are usually pretty good, boiling it down to spur gears having straight teeth and helical gears having angled teeth.beyond that simple description, it seems like the angle on helical gears helps them mesh more smoothly and quietly. Instead of the entire tooth surface hitting at once like with spur gears, the contact starts gradually. does anyone have experience where the noise difference was really noticeable? I'm curious about real-world applications where that smoother engagement makes a big difference, like maybe in machinery where even slight vibrations could throw things off. Or even in automotive applications - I'd guess helical gears are more common in transmissions now for noise reduction?