How do you choose a powder?

So I started reloading late last year/ early this year. I started reloading for my .308. Everyone raved how accurate Varget is, so I started with Varget. I worked up a really nice load with the Varget and really haven't seen a need to change for the .308. I bought a pound of BLc-2 and Win748 to try, but I am shooting .500" CtoC 5 shot groups at 100 yards all day with the load I am using, so I haven't even opened them.

When I start looking at 6.8 loads, it really looks like everyone is shooting just about every .270 bullet with a wide range of powders. How do you pick one to test. What exactly do you look for?

I was at a local reloading shop and they had some 110gr pro hunters, so I picked them up, with a set of dies, some Reloader 10X and some RP brass. I know RP brass doesn't get good reviews, but I have a ton of large primers, and I am not paying todays prices for some small primers.

I picked the 10x because I saw a nicely shot target posted on here and the guy said he was using Reloader 10X and 110gr. Pro Hunters. Thats the only reason I chose those for my first attempt. How else would you find a good powder?

Thanks
David