What it boils down to is when do you expect to upgrade again, as if you go with .0 version then your lifespan is about half of the .5 release. So, you'd expect to upgrade 12.0 sooner than 11.5. With that being said if the features of 12.0 are appealing to you and you understand the change to Smart Licensing and deprecated phone models (both 11.5 and 12.0 deprecated some models) are not concern to you then it is a solid path. Also, make sure all other applications in your environment are compatible and plan upgrade of those accordingly if necessary.
