I usually wear an 8 in street shoes, sometimes an 8.5. I ordered an 8.5 in these in black and they fit perfectly. I also own a pair of LaDuca 2.5" Elizabeth heels in their size 8 tan, as well as pair of LaDuca Annie boots in size 8.5 black.
To compare:
1) The So Danca shoe is a little bit wider in the toe and therefore more comfortable for me. I think my size 8 LaDucas may be just a smidge too small.
2) The style of the So Danca heel honestly makes it look a little taller than 2.5" in my opinion, which I like.
3) The So Danca is just as flexible as the LaDuca if not more so (for better or for worse).
4) The leather on the LaDuca shoes is definitely of better quality than that of the So Danca, but no one will be able to tell from on stage. However, I'm not sure if the So Danca would be able to stand up to the LaDuca over time/last as long.
I like both my LaDucas and the So Danca for different reasons, but the So Danca shoe is definitely a good buy.