I use 4064, but a lot of the guys I know who are much better shots than I use Reloader15.
Either powder will serve, I think that Re15 is the powder used by more competitors in 308 and 223 now.
If you don't mind keeping a log book of changes including temperature, there are still some folks who use 4895.
I would not choose 748 for an accuracy load unless you needed a ball powder for use on a progressive reloading press. And in that case I chose Power Pro 2000 MR for my 223 match load, and I am happy with the performance (PowerPro2000MR is pretty temp stable based on measurements someone else took over at snipershide).
Machine guns are awesome until you have to carry one.