Hi Style, I think it depends what type of do it is, and what else you want to wear, what colours suit you etc
The Karmel dress is very pretty with interesting detail, but you would be showing your arms so may need another layer?
The Ruby dress is classic and bright- really stands out but still chic imo
The blow her away is fab, again really stands out, especially if you have great legs and will wear some killer heels, but is less classic, more fun I think?
The Noli dress is a gorgeous colour, but could possibly look the least dressed up of the lot of them, I think you would really need some funky accessories with it.
You could wear the James one with some spanx type underwear to give you more feeling of structure, it is understated chic and would look blinding with some sock it to 'em shoes and jewellery.
So, it depends what you want to convey ir
If it helps you could wear the Karmel, James and the Noli in the daytime out to lunch, whearas the other two are more definite night out dresses to me. This may be an advantage or a disadvantage, depending on your viewpoint.
Eeek! Haven't been much help there have I!