It is possible to choose not to have an external siren to your alarm system, then I would consider a self monitored or back to base alarm system.
Power consumption, it is a known fact that the new LED siren light will draw less power than the conventional strobe.
In short, if you power goes off and you have to rely on back up battery. The LED siren will last the longest.
If it is possible choose the large siren box with multiple indoor sirens to provide the loudest alarm siren and deter potential intruders.
Siren boxes with red lights are not available in Australia, blue light is the preferred colour for a siren box.