It looks close to me but I think the brunette is surprisingly bigger.
Sidney is thicker overall, so her tits don't stand out as much. Alexandra is very thin, so much so that she was asked to gain weight to do the Baywatch movie, so her tits look that much bigger on her frame. Alexandra is also 5 inches taller than Sidney, so that makes them that much more difficult to compare. Online listings have Sweeney at either 32D or 34D, while those same listings have Daddario anywhere from 32C to 32F. Just comparing what I've seen, especially the most recent stuff, it clearly appears Daddario is bigger but it's not by a lot.