Well, I've heard the term cradle used for 2 different things, one is like an engine stand only a cradle usually sits a bit lower to the ground and is not rotate-able, and the second term is the subframe that holds the entire motor into a car, most newer GM FWD vehicles have a separate subframe that holds the motor in (and usually the 2 bolts on the rear rust out and drop the motor from the car)
Hey DC , welcome to MM. It has been my experience a cradle is a good way to store an engine under a workbench. too low to work on. Engine stand is better. Higher, lets you rotate engine. If you are asking about engine cradle used on vettes for frame stiffening,
kennybrown had a tutorial about stiffness on his website. Hope this helps.