If you already have lighting on your property, you may want to keep the same color temperature throughout (It can look strange to use different color temperatures among nearby lights)
2200K: Very warm (similar to candlelight) and can be used for special romantic effects in patio or deck settings. This light is also close to the color of sodium lamps used in some streetlights – so designers may want to match that effect.
2700K: Most commonly used in landscape lighting (very warm and welcoming).
3000K: Preferred by some because they like the cooler look especially when lighting vegetation.
4000K: Sometimes used for downlights from trees, because it is similar in color to moonlight. Others prefer warmer colors for those lights.