There is no one that can answer this question for you. If I said, "I tried both and, in six months, I had $1,043,434 in USD donations and 1 Bitcoin", does that help? No, because it's "general information", not specific advice/data from the same audience as yours. If you're building a blog for people over 80 years old who want to check out their health insurance options in the US, obviously USD. If you're designing a tech review site for bleeding edge folks, maybe then BC. But unless you know your target audience's desires/comfort level, there's no way to answer this.
As others have said, offering both is a good idea. Unless you scare people by offering them choices they don't understand (many 80yo people don't understand BC and you might risk losing any donation from them if you paralyze them at the donation level).