So I just came out of this. I do think it's worth a watch, even if you've seen the NYCC/Broadway production (which I've seen four times). IMO, the Broadway production is better, but there are aspects of the Signature production that I quite liked. (Not Milky White -- Kennedy Kanagawa's Milky White >>>> all other Milky Whites.)
1) I like that the Signature Narrator is a bit more dynamic (moves throughout the stage for the entire show) than the Broadway Narrator. (That said, David Patrick Kelly's gasp-runs are hilarious.)
2) In the Signature production, Cinderella's Father is portrayed as a drunkard, so his treatment of Cinderella makes a little more sense; I never quite understood the source of the Broadway Cinderella's Father's callousness.
3) Don't @ me, but I liked Phylicia Rashad's recorded Giant better than Annie Golden's modified live voice.
4) I am going to get kicked off this board for heresy, but Erin Weaver is a better Baker's Wife than Sara Bareilles. Sara B. has the much better singing voice; Erin's range appears to be more limited. But I felt that Erin stepped into the shoes of the Baker's Wife in a way that Sara B. did not. Also, the chemistry between Erin and Jake Loewenthal (who was also excellent as the Baker) - this was probably the best Baker/Baker's Wife duo I've seen. (n.b.: I've only seen Sara B. + NPH/Brian d'Arcy James, so it is not a long list. We are obviously not counting Corden/Blunt.)
4a) That said, Sara B.'s Baker's Wife has a soothing/therapeutic quality that Erin Weaver's Baker's Wife lacked. Listening to Sara's "Moments in the Woods" makes me feel like everything in the world is going to be OK.
5) I found Katie Mariko Murray's portrayal of Cinderella to be more complex than Phillipa Soo/Denee Benton's. I would give Phillipa Soo the edge on comedic delivery, but Katie's "No One is Alone" had much more depth -- truly acted through the song.