On first impression I would vote [name_f]Anna[/name_f]. The ‘gusta’ in [name_f]Augusta[/name_f] is not my favourite but the more I think about it the more it grows on me. It’s the quirkier choice which I like but strangely I prefer [name_u]August[/name_u]. Not very helpful, sorry! 
[name_f]Augusta[/name_f]! [name_u]Gussie[/name_u] would be adorable.
[name_f]Anna[/name_f] is classic and versatile and I feel like it’d fit many different personalities, whereas [name_f]Augusta[/name_f] may be difficult to live up to in my opinion, I can only imagine a quirky/artsy yet confident kind of woman, and I can’t picture it on a little girl at all.
Both names are great, but with [name_u]Douglas[/name_u] as the middle name (and a surname that might begin with an S?), I prefer [name_f]Anna[/name_f]. [name_f]Augusta[/name_f] makes the full name seem kind of “s”-heavy.
I’m another who much prefers the elegant [name_f]Anna[/name_f]. [name_f]Augusta[/name_f] doesn’t appeal to me at all, however I don’t mind [name_m]Augustine[/name_m] and [name_u]August[/name_u] for a girl - which is a bit odd I know as these are traditionally boy’s names (I prefer the variations of [name_m]Augustus[/name_m] and [name_m]Augustin[/name_m] for a boy).
I [name_u]LOVE[/name_u] [name_f]Augusta[/name_f]. It’s been one of my favorites for about 10 years now. [name_f]Augusta[/name_f] is so packed with vivaciousness! [name_f]Anna[/name_f] seems kind of ho-hum in comparison.
I really like [name_f]Augusta[/name_f], and I enjoy [name_m]Augie[/name_m]/[name_f]Aggie[/name_f] and [name_u]Gus[/name_u] as nicknames.
[name_f]Anna[/name_f]'s nice, but I feel like I’m hearing it a lot on babies where I live (especially when I factor in the [name_f]Anabel/name_fs). [name_f]Ann/name_f feels fresher to me.
Whichever you choose, she’ll have a lovely name with history and gravitas.
I have an [name_f]Anna[/name_f] myself and have enjoyed reading all the lovely comments about her name. I chose [name_f]Anna[/name_f] for its timelessness. It is a name that can’t be pinned to a particular decade.
That being said, I think [name_f]Augusta[/name_f] [name_u]Sinclair[/name_u] sounds great–regal and distinguished. Maybe a teeny bit hissy as someone else said, but still a wonderful name. I expect you will get many compliments when you introduce a baby [name_f]Augusta[/name_f]. I don’t get many compliments on [name_f]Anna[/name_f]'s name because people have heard it so much.
Best to look into your heart to ask yourself which name you love best. Which one do you love to say and see written?
I prefer [name_f]Anna[/name_f]. [name_f]Augusta[/name_f] is a decent name, but I feel like it sounds kind of old timey. [name_f]Anna[/name_f], on the other hand, is timeless and pretty.
[name_f]Augusta[/name_f]. I don’t even mind [name_f]Augusta[/name_f] [name_u]Douglas[/name_u]. I might be biased because i grew up with a lot of anna/annabelle/annalee/annalynn s. [name_f]Augusta[/name_f] is my grandmother’s name and don’t hear it often. She is the coolest /quirkiest lady i know. 93, can out walk any of us at the zoo, and walks her ducks on a leash. [name_f]Augusta[/name_f] ([name_u]Gussie[/name_u]) is one of my favorites
My choice is [name_f]Augusta[/name_f]! It’s fresher than [name_f]Anna[/name_f] [name_f]IMO[/name_f] and goes better with [name_u]Douglas[/name_u].
I love [name_f]Anna[/name_f]
[name_f]Augusta[/name_f] is one of my top choices for my own daughter! I think the full name is strong, elegant, and uncommon without being “out there,” not that there’s anything wrong with “out there.” I love the nickname potential: [name_f]Aggie[/name_f], Auggie, [name_u]Gus[/name_u], and [name_u]Gussie[/name_u] are all quirky, spunky, and kind of artsy/earthy to me.
[name_f]Anna[/name_f] is sweet and classic. As one pp pointed out, it might read as the more feminine option alongside mn [name_u]Douglas[/name_u], so if that is something you are considering, well, there’s that. I like [name_f]Andie[/name_f] as a possible nickname for [name_f]Anna[/name_f] [name_u]Douglas[/name_u].
An old favorite of mine was Andalusia, which you might like.