Let both vendors show you samples of the flowers they could use on your dress..
Negociate about price..
Thay both won't give you 100% exact replica of the dress..
But I saw a recent Millly dress that looks so much like Mounique Luihiller Floral dress & I saw D have a replica of Rhianna Royal with nice flowers..
Here're Duosheng's flowers: Rhianna Royal, Another Dress
Milly's: Mounique's
Is Duosheng's quote on High quality?
I'm leaning towards Milly because they made me a wonderful dress..

Give them a closer date for the wedding, Just let's say, tell them it's in first week of July..
Again, ask them to show you flower samples & talk down the price...
Good luck..