I prefer the bluer daylight versions myself, but for your outdoor
security lighting, consider small 35W halogen reflector floods. I
illuminate my entire back and side yards using four (two in each
fixture) motion detector flood lights equipped with these, and they are
plenty bright enough, can be aimed DOWN, away from the sky, and last
well over a year on the motion controls. You definitely want whatever
you install outdoors to be a controlled illumination pattern. No sense
wasting power to light the sky, or the neighbor's property, and
contributing to light pollution.

RPS wrote:
I have to make some decisions about lighting the lobby of a six-flat
building, stairwell, hallways, back porches, as well as a security
light for the yard.

The basic decision is: do we go with old fashioned warm yellowish
lights, or the new cool "bluish "daylight" types?

Any suggestions or experience appreciated.