Generally for lawns we recommend Hunter Industries MP Rotators. They save around 30% on your water bill and require less infrastructure to install as the reduced flow rate allows more sprinklers in a zone. Watch the youtube video below to find out more about the MP Rotator.
However, there are always exceptions.
For example, if your sprinklers are attached to a bore, the system design should be about maximising the water throughput within the paramaters of your pump. Often bore water is dirty and in certain circumstances can causes issues on low flow sprinklers.
Another way to think is scheme water is expensive and charged by the volume (kilolitre) whereas a bore uses electricity and therefore minimising run-times may deliver a more efficient system.
An irrigation expert can help you navigate through this prickly path and help you determine the best solution for your sitation.
Hint: Cheap sprinklers are cheap for a reason. They can end up costing you more in the long term and requiring continual maintenance. A good sprinkler body and nozzle will cost around $8 to $25 depending on the type.