The difference is that the device is liable to any returns or insurance policies per the third party (aka best buy,
Meaning when verizon says that you have 30 days to return or exchange a device,
this may not hold true for best buy or walmart.
They do not go by verizon policy on this.
It will list in their terms and agreements what their policy is,
but usually it does not match up with Verizon themselves.
Other than that,
such as service with your phone and plans remain the same.
The equipment is all that matters in this case