BL-C(2) is at the top of my list as is CFE223. Both provide absolutely top velocity with 150/180 bullets and great accuracy.
I have made up some 308 loads using CFE223 and it seems to produce pretty high pressures. Not sure that one would be a good choice for 303 case longevity. BL-C2 published pressures are typically lower than other powders yet it produces good velocities. I am seeing single digit SD's which is impressive.
I've always used IMR4064 with 174gr Sierra's. Works well in all my LE's