Agree with VR.
In addition to that, if you are using cluster features & your older ESXi host CPU is different from new ESXi host (Intel vs Intel OR AMD vs AMD etc). Straightforward vMotion will not work. You will have to enable EVC on cluster. Refer:VMware KB: Enhanced vMotion Compatibility (EVC) processor support
VMware Compatibility Guide: CPU Compatibility for VMware VMotion