The halophosphate Kr filled is exactly what most T8's here are - 36W (direct retrofit to 40W T12 on Switch Start and Perfect Start), Kr filled, Halophosphate 6500K, CRI ~70. I like them very much and dont see anything wrong with their colors

And i dont see any noticable difference between their color and Ar filled T12s with the same phosphor

Ash: You can see that the krypton T8 consume less wattage than the argon T12 (36W vs 40W). Also I noted that krypton T8 here, are slightly brighter than the T12s. Krypton T8s are more sensitive to lower environment temperature than T12, and krypton T8 takes 2 mins to warm up (They start out with ~90% from their full brightness, but this isn't so noticeable for most people), while T12 start at full brightness instantly. And finally, krypton T8 have higher starting voltage, limiting them to preheat/perfect start or electronic ballasts. These are all the differencies of the T8.

Brightness : color 765 T12s and T8s are about the same in Lm output. (Some T12s have like 200 Lm less rated, but some degrading or lil' mercury starvation will easily get any lamp to 200 Lm output drop, so its not big difference)

The visal brigtness (what you see whan you look at the lamp) is 1.5x higher in the T8 since it emit the same amount of light with 2/3 of the surface area of the T12

The new F34T12/835 alto lamps are much better then the older ones they also are available in /841,from what I've seen they have fixed the mercury starvation problem. .  at work we use 57W /841 lamps, they're brighter then the 60W halophospate 8ft lamps! But the full 75W/841 Sylvania lamps work the best when it gets cold in the back room
We even have a few lights with 60W /835 Sylvania 8ft lamps