I’d say it’s one of these YMMV issues that depends on the shape and size of your ear canals, how good an impression your provider makes, and who makes your molds . Domes are made in a fixed set of sizes to a regular geometrical shape and the attachment point at the base on a tulip dome can be an odd, poor fitting solid object in your ear canal in spite of the ability of the tulip “petals” to accommodate various canal sizes. I had my molds made by ReSound and they follow a 16:4 rule, the mold from the entrance to your ear to the inside should be at least 16 mm long and go 4 mm past the first bend of your ear canal. If one has any waviness or undulations in the shape of your ear canal(I do), the mold captures that and the uneven mold shape forms a grip to hold the molds firmly in place (my molds do not slip in the least - but whatever dome I wore did not either, as I used concha (“sports”) locks when I wore domes). The undulations that I’m talking about can be seen in the shape of my right mold in the linked picture below, as well as a notch in the mold near the point of receiver insertion (red arrow) that appears to catch the crux helicis above my ear canal and also help hold the mold in place. In any event, one (bird) swallow of any sort does not a summer make, but looking over many posts on the forum, especially with severe hearing loss, most people who are willing to go to the extra expense of having good molds made get pretty satisfactory results and as far as trapping low frequency sounds within the ear to prevent loss of amplification when you most need it because of severe loss, molds offer a thickness of material compared to domes (don’t know about click sleeves) that better traps low frequency sounds within the ear canal. Works the other way, too. Because I’ve chosen an occlusive mold, when I want to block out extraneous sound, I turn my HA’s down or off, and much less outside noise comes into my ears with my molds in place than I’d hear if I were wearing tulip domes or power domes (again, have never tried click sleeves).
Should emphasize that good custom-made molds fit your ear canals perfectly, as mine do.