Not sure what company you are dealing with - I sell Emtek and the rosette does not factor into the price at all. The handle/lever and finish are your price factors.

I like the square one better, personally

I chose Round...if they loosen up a little, they won’t get wonky like the square. Constant issue with my square rosettes in my last house. Although I have to say that I do not have that issue much with this hardware which is Emtek compared to my last house..Bravura.

I was going to type what ilovered said- square or rectangular can shift with time which can be annoying. Otherwise the square is more contemporary, round is more traditional.