I use half checks on our two.
I find them easier to control than a flat collar. On a flat collar I can't correct them, whereas with a semi check I can
I have them fitted so if you hold the nylon part, they can slip out, but if you tighten the chain, it is about the size of a normal flat collar (still able to get fingers underneath). Mine could probably do with being tightened so they check easier, but as they are almost always walked on a harness or headcollar, I just leave them looser
Something I prefer about the semi to the full check is you can't put them on wrong lol.