guess it really depends on the situation. We have had LL's request the more 'sales' type boards, or some of them might be dual purpose boards with an overlay on them that once the property has sold you can peal off the 'for sale' part and it says 'for lease' underneath... auction boards are like this too.
We also tend to use them for high end properties - at the moment we have a $2000 per week property in and area known for the boards being destroyed by passing 'happy' people on saturday night so we have paid to have a proper board installed above ground level on the house - looks much nicer than a core flute sign and is tougher to withstand potential airborn attacks.