Please can anyone tell me which is better?
Using VTP on switches or
Configuring vlan manually on switches?
Bearing in mind we only have 6 switches.
There are pros and cons for both.
Using VTP means you only have to add the vlan to your VTP server switch and it is automatically propogated to each client switch. Hence you are less likely to forget to add it to a switch.
However if you want control over your setup you should go transparent. There is no danger of introducing a switch into your infrastructure and accidentally wiping out the vlan configuration. Also you only add the vlan to the switches that need it.
It comes down to convenience (VTP server/client) versus control (transparent).