I am fairly happy with my buttonholes on the whole, but there is a fundamental difference that I see with professional ones and I can't work out what I am not doing quite right.
Pictured below are 1. One of mine and 2. One on a velvet Savile Row DJ I have (not made for myself sadly):
The stitches seem much tighter, closer together. It's also much stiffer. The thread might also be finer I think?
If I try to pull stitches tighter it just makes the hole deformed. Any ideas?
The first I learned about hand made buttons is to use two strands of buttonhole twist. Lay them side by side. On trousers they are more flexible. A business suit gimp might have the best appearance, sometimes. A sports coat is very different coat. I would think for most a softer buttonhole.
Whatever the customer wants. It's theirs.