I dealt with vehicle deliveries for years, the main reason transport companies use the frame tie down method is to lower the vehicle so they can drop the upper ramps and reduce overall height of the transport truck. I've seen these tie downs cut through the uni-body sub frame on more than one occasion, and elongate the frame holes on P/Us, bouncing makes them work like a manual can opener.
JMHO. For your personal vehicle I'd say go with a wheel tie down, similar to those used on a car dolly.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.