From an aerodynamic point of view, it depends on what is the factor setting V2. If it is limited by stall margin, then 15 degrees is a hard limit and any OEI proceure that requires more also needs to schedule a higher speed, with associated penalty for acceleration distance. This can vary from runway to runway and day to day, so in order to have a consistent policy the norm is to always select 15 degrees except at some specal airports that would normally require specific training.