Definitely commissioning a custom for me, but I won’t say no to a YCH every now and then

It varies a lot for me on budget. Ychs tend to cost less because they are made with pre-existing assets. Ychs are also a nice way to introduce customers to your style. A custom commission tends to cost more but is more personalized. I personally try to commission a custom only after I've worked with an artist for a bit. That way they have a feel for my character and it's easier to understand their limits. Cause in the end what matters to me is the artist enjoying the character as much as me.

I prefer custome, but I am always full of ideas, very happy to be super specific, draw crude examples (cause I can't draw well) and nitpick the heck out of wip, often get grumpy when artists I work with move too fast cause I don't want them to undo lots of work for fixes, once the sketch of line work is of sufficient quality. then I give thumbs up to move to colouring and such, knowing I won't allow myself to change the lines anymore, etc
but I suspect most people ain't as imaginative or nice to work with (either they too demanding or they too shy to point out issues) as me, so they prefer YCH...
so ideally you want a mix! or like I did with zombineko, turn my custom art into YCH, one of them actually became 2 cause she got the pose, POV and such all wrong in the first sketch,