well, I own Granville, and the fact that I love it is because its lambskin, so smooth and slouchy, White ostrich would be very hard to take care of and in long terms, ostrich tend to get wrinkle especially the Granville is not quite structure bag. If judging from the two model, I'll definitely go for Granville, but when comes in these two leathers, I'd go for Lady Dior Python.. it's a truly classic, shape and color.
The ostrich is a divine skin on the Granville, but it will be an absolute nightmare to maintain in white. I'd go for the python Lady Dior, an emblematic bag in a very noble skin. Plus, the bicoloured hand finish makes it all the more desirable.
I would get the Granville! I love the cross shoulder and slouch it has, while you can also wear it up and its absolutely beautiful and elegant too! (besides, im partial to the brighter python colors they have...)