It's all in the title. I've never played a headless-- Why? Because I think they're gimmicky and I generally dislike their look. Not discrediting anyone who likes them. I really, REALLY want to learn to love these things, but they look like a baseball bat with a slab of meat at the end. What's so good about these things other than them being lighter?
to me they’re the opposite of gimmicky, they are purely about improvements to standard headed instruments.
I think for many people, or at least for me, I prefer the look of a headed bass, but feel headless is just an improved design.
Here’s some things I love about them:
The big one is that they don’t neck dive on a strap. Perfect balance.
Another practical feature is they are smaller overall, so easier to store, transport and wield in a cramped space
Generally stay in tune better, all else being equal
Generally lighter in weight, all else being equal
Tuning at the bridge is more comfortable, at least for me, especially if one has shoulder issues, as I do
When they have the cutout for the bridge, you can lean them on an amp with no need for a stand. usually.
Sounds silly, but this is handy
Cons:
looks
people coming up to you literally at every show asking if your hand slips off the end, or saying “hurr durr I think your bass is missing something” and thinking it’s funny and original