I don't think Butler and PG are on the same level. PG was regarded as a top3 defender at his position for many seasons and has been very consistent as a go-to scorer. Butler is a good defender that sometimes have 40-50pt games. I'd go all-in for PG, but not for Butler.
Oh, yeah, and there is the cap matter. Going for Butler meant NOT GOING for PG, as going for Cousins did.
I consider PG to be a boardline top10 player. He won't put the Cs over the top by himself. However, in case Danny intends to go after a top5 player (hi, Unibrow!) it would be great to sign him (w/ an extension) now. He could be later used in a trade for a better player.