26 is indeed more temp-stable than 25.
One thing I've learned recently from conversations with various people in the powder industry that relative burn rate is becoming an really iffy term these days, with all the super-progressive burning powders appearing. An example would be, say, a new powder that from its listed powder charges in various cartridge/bullet combinations looks like it burns about like IMR4895. But it has a far different pressure curve, more like one of the 4350's. And in fact one of its characteristics is providing 4350 velocities with lower charges, because it's so progressive.
Which is yet another reason burn-rate charts aren't all that accurate.
