Is there even a difference? The answer is yes. I tend to use them interchangeably, but the stretch needles do have some benefits for the extra stretchy fabrics like lycra/spandex.
Both types have a rounded end compared to a universal needle, which prevents snags or runs in the knit fabric. But a stretch needle also allows for a longer thread loop, which is supposed to prevent skipping stitches.
So if you’re using lycra/spandex, I would go with the stretch needle. And when in doubt, take a scrap of the fabric you’ll be using for a project and test out the stitches with various needles to see what gets the best result.
Thank you for this! I’m about to jump into making my 1st swimsuit and had some questions about that.