Because over 150W one needs to get permission from council etc it is unusual to use any security lights larger than 150W. The problem is of course discharge lighting does not like being switch on and off all the time so if PIR switched the tungsten is still used. But a 150W tungsten lamps is about 30W in discharge so first one has to consider how long it will be on for. Clearly if over a 1/5 of the time it is on then may as well use discharge lighting and leave it on all night. There are a number problems with the humble PIR. Cats can set them off. They can be set off by neighbours lights. They can be set off by radio transmitters. Clearly all these will be dependent on where the light is used. So a light which is A1 in one location may be useless in another. I removed my PIR for a photo cell and use a small discharge lamp 8W on all night long as it was like Christmas where my neighbours lamp if activated would in turn switch on my lamp, that would then switch off my neighbours lamp. But as soon as my lamp went off that would re-active my neighbours lamp. On Sizewell "B" power station we found when the photocell on a crane failed and the lights were on 24/7 the tubes lasted longer then when switched on at night only. So not sure if quartz halogen is really any good for a security lamp. Infra-red lamps with infra-red cameras is likely best option. Go for full 1984!