Interesting thread. My first use of dynabar slider was a WOW moment ... the freeing up of hips for toeside riding felt amazing, I was sold immediately. Now with more foiling, even more sold on sliders. With more acute upwind angles, especially toeside, I find the fixed hook feels restrictive.
In the kite surfing community in past years, the benefits of a moving hook was accommodated by leaving waist harness loose, so the entire harness effectively becomes a slider (see early Ben Wilson instructional videos). Which is a much less efficient way to achieve this, when the harness is built to accommodate your lumbar. The tipping point seems to be the rise of Ride Engine as the go-to cool brand for surf focused kiters. Their fixed hook is an after thought, they've always been about a slider ... and as simple a system as it gets, chicken loop on rope. This seems to have taken off ... and lately it seems to be generally agreed for those primarily seeking waves, that allowing some movement of the attachment point is a good thing. Though maybe not for the GKA types, where airs a big part of the repetoire, and a fixed hook is beneficial for that.
I think the slider has to be smooth to be effective and satisfying. The Da Kine one where the slider is on the webbing is too jerky. The chicken loop on rope is also too jerky, plus wears out the rope too fast. Now that my dynabar slider finally broken (4-5 years of use), I now use a steel carabiner between the c loop and rope, works well and allows for leashed self launches and self landings. There are nice stainless yachting gizmos that do this very cleanly, as well as giving potential to get rid of c loop altogether -- as it becomes redundant without the hook it is designed to clip onto. But that's mad scientist stuff, a whole 'nother thread!