The T8 is on the left with 3500K Philips Alto II lamps and the T12 is on the right with cool white GE made Doit lamps on a full power ballast. the T12s are a tad brighter but not by much.
The T8s are triphosphor and the T12s halophosphate , i think a more accurate comparision would be with the same color temp T8 &T12s with the same CRI, but cool experiment anyways
So those are triphosphor but it's a good comparison anyway since that's what modern T12s are (like what a fixture in a lighting setup retrofitted to T would probably have by now (halophsphate tubes made before 1995 long since burned out).
yeah the tubes in the preheater at my mom's dad's shop are newer pre-eco lux 40W GEs. possibly residential grade... the industrial f40 rapid start fixtures in my dad's parents' house still have True Value tubes which are liekly halophosphate since they're a bit greener than the lamps i see today. almost like an old /DX merc.