When I saw Taye's first show, I was in the middle of a pack of women all roughly 40-50. Several said they'd been Taye fans since How Stella Got Her Groove Back and that movie is at least 15 years old now. I don't think Diggs has the same kind of fan base that other Hedwigs have had, but I think his return to the stage is incredibly appealing to the almost middle age group. I think how well known he is really depends on where you're looking and asking. My non-theater friends (all between the ages of 25-40, approximately) know him as "the guy from Private Practice/Grey's Anatomy."
Each Hedwig has had their own fan base that come to see the show just to see them perform. I think Taye definitely has that. People recognize his face, if only because he's had smaller parts in so many projects. Asking who is more popular isn't really worth it, as it all comes down to who you're asking. If you're 17/18 years old, I wouldn't suspect Taye Diggs to come up as an important or relevant actor, just as Darren Criss may not be relevant to a 50 year old. Or Andrew Rannells may not be relevant outside of the theater community. Arguing over which actor has the most fans takes away from the show--to me, that instantly makes it about a person portraying someone. It's no longer about the characters and the stories they tell.
Moving on...
I think Amazing Grace is on it's last legs. This week's numbers show what what people have been saying all along: the show just isn't finding an audience. I know they're still comping, but even that isn't getting butts in seats. When I saw the show in Chicago, it struck me as something a televised MegaChurch would create. Nothing about it screamed Broadway, aside from casting a few known names in the theater world. And pretty costumes. But well known names and good costuming don't typically keep a show open. In the worst of shows, the actors are often doing their absolute best with what they're given. This season, I can think of at least 6-8 musicals that are working their tails off for a theater, but simply won't get one because of availability. Every show deserve it's chance to shine, but I don't feel like Broadway is the right venue for Amazing Grace. In my eyes, it's taking up space that that is greatly desired and could serve other shows better.
Amazing Grace could do great in other productions--I truly wish it the best in the future, but I think it's a future of regional productions and Christian colleges.