Hello Madhu
I went into the lab and attempted to use both the show bgp vpnv4 unicast vrf CUSTOMER summary command and the show bgp vrf CUSTOMER summary command and both resulted in the same output. The more correct command to use would be the latter since it specifically states what you want displayed.
The show bgp set of commands tend to assume certain things when you use them. For example if you simply issue the show bgp command, it will assume the ipv4 address family. In this case, there is only one VRF, so all configurations are assumed to be in that VRF, and thus both commands will result in the same output.
I hope this has been helpful!
Laz