Varget is a slow powder for .223rem, i think you'll find it hard to fit any more powder in a 223rem case, than it is to go over a max loading(max charges listed state it's a compressed load for 69-70gr bullets)
As you are using a heavier bullet than a standard loading for 223rem, if you don't have a super short 16" barrel and if the twist rate is suited for longer bullets, then the slower powder with longer bullets is good choice in my opinion.
But it all boils down to wheather it puts results on the paper/target with particular loadings, with your rifle/load combo.
I like Varget for my 243win with 70-85gr bullets for it's clean burning and consistant quailities.
Just my thoughts though.