Also - when you are "moving" the VMs cold it should take no time at all as long as you are not moving across storage. Just changing the ESXi host will be ~1-5 seconds of registration time as that is what you are essentially doing, i.e. unregistering and registering again under the guise of vMotion.
As to the other - its as mentioned. The processor instruction set is different enough between the hosts that what ever is configured on the guest would not survive a vMotion.
From what you have said, all the VMs were initially powered up on the same host so in theory should have the same instruction set applied. In practice there are other things that can determine this with one being the VM hardware version. For example: in our environment I have some VMs (running HWv7) that are running as "Westmere" whereas HWv8 machines are "Sandybridge". The EVC cluster is currently configured as Sandybridge. Is it possible you have different VM HW versions? Are VMware tools all the same version?