I'm certainly no expert, but I think those types of ratchets were designed for spark plug service. My opinion is based on absolutely zero scientific fact, but more on my own very limited experience. That being said, I find myself using an old Craftsman 3/8" drive, long straight (not bent) handle, flex head ratchet on spark plugs. Admittedly, I think my old Craftsman would provide a little more utility if its handle was bent, that way, the lower portion of the handle, closest to the socket, would remain somewhat perpendicular to the work (in my case the side of the engine block). Consequently there would be less flexing of the ratchet's head and less of a chance that the socket would slip off the plug, thus damaging it. Having a bent upper handle would provide me with a little more knuckle/hand clearance too. I keep saying I'm going to buy a bent handle ratchet, but find myself resorting back to my old Craftsman instead. For the couple times per year (at most) that I find myself servicing spark plugs, it's just easier to use what I have. If I was a pro, I'd most likey have one. Still, if I ever came across a good used one, I'd jump on it.
Jim C.