Your direct cable is clean dependable power and copper wire is low resistance. A vehicle chassis is a poor conductor and subject to corrosion and other failures. Just bad practice.
I can’t tell you how many utility trailers, boats, and campers I’ve chased electrical problems for.
A proper independent ground cabling system almost never has issues and they’re easy to locate if they do.
Chassis-common ground issues can be so elusive and time consuming. And frequent.
Clean home-run grounds are safe and durable.