Very good points, penguin.
You are right in the sense it probably depends of the setup what reflective layer to choose.
Reflectix keeping heat in the room is a advantage in some setups, specially in large rooms, but i believe its a disadvantage in cabs.
I painted my floro's reflectors with thermal resistant enamel+barite and i noticed a large improvement since it: although the lamps are at the end of its useful life, im getting higher yield for it.
I prefer painting than attaching reflective surfaces, but this is just my personal preference. Anyway, the white paint+barite option is another excelent option, wich havent been used and worth to be considered.
As said before, barite is very cheap, and its just mixed with latex paint to increase its durability.
In this pdf you can see reflectance and durability analysis of different white paint+barite mixes. Instead of using pure BaSO4, wich is more pricey, i choosed to use barite, wich is 93-99% BaSO4 (96% for the barite i buy) and is very, very cheap. Likely this weekend a friend is going to test this cheap mix with a spectroradiometer, in order to see if using barite instead of pure BaSO4 has an impact on reflectance and how much.
knna