Congratulations! I think the 53 is best because you can adjust the seat easier than the top tube. As you say, there is something to the geometry of the Diva that just makes it fit better having been on the Orca for nearly 2 years. Good thing you have that hot orange Orca to keep up with the Diva - watch out!
About the color-I originally ordered the blue(in fact I'm wearing the blue Terry jersey my friend gave me to match my new "blue" bike) and the shop said it takes 10 days to get it in. Two weeks later they called and said to pick the purple or green, shortage of blue at the time. All the Orbea colors look good.
I looked at plenty of other bikes too, but none of the women specific or others are as light as the Diva and didn't seem like they were going to be an improvement ($3,000-$5,000 worth)on the Orca I had. Looked into a Seven and Calfee last summer and the price nearly doubles plus would not have been ready for a Colorado tour we did last year. Ridin strong on my Diva is what they're just sayin'.