Get a quote for both covers.
Comprehensive can work out the cheapest option as its the only cover that allows a age of car discount so if it a older car.
Depends on you age also.
If your married and the wife has a licence put her on as it may reduce the premium. Stange but true in some cases.
Also I would always recommed using a Broker, if it goes wrong or you have a problem they are there to help you.
You can have comp cover on cars worth less that a £1000.
HTH