In OEM applications, those nylon clamps are usually used only in low pressure, non-critical applications like a hose for the coolant recovery tank... or the occasional emissions hose. Not a good idea for transmission cooler lines IMO.
Personally, I would prefer properly sized spring clamps. Problem is that those are hard to find- particularly in the exact size that you need for a given type of hose.
So as a practical matter, I just use standard worm-gear clamps in this sort of application. As long as you buy a good brand (not China junk) and install them properly (don't overtighten), they'll work fine.