Hi,
I would recommend having two switches configured in VTP server mode for resillience so that if one of your VTP server switches fails you still have a second VTP server.
All the other switches i would configure as clients.
The pruposes of VTP is to propagate VLAN information through a layer 2 switching domain and controlling this information from a central location. If all your switches are in server mode then there is more scope for errors made to the VLAN configuration which would be propagated throughout your switching domain.
HTH
PJD