KME provides more services on the background then ZT, you might want to keep that in mind.
Every Samsung phone comes with a warranty bit, a one time efuse that checks wether a custom kernel has been loaded to the device or not. When that happens, the fuse will change value permanently. KME checks that fuse, so if there was ever any tampering with a device, it will not enroll trough KME. It gives you some peace of mind knowing that devices contain the original hardware.
Besides that, I believe that KME also checks other firmware related stuff and blocks enrollment when it doesnt trust it.
They perform these checks in the free version as well, you don't need to pay for the advanced KME features.
I advise customers to use both in these kind of scenarios. One platform would be better in most cases, but this security check is worth the extra platform in my opinion.