I think it's foolish to say Brianna is trendy and Briana isn't. They're technically the same name.
I prefer the Brianna spelling over Briana. Briana just lookes like Brian with an extra a tacked on the end. Brianna looks better.
I like Brianna more than Breanna.
My cousin had a girl and called her Breeanna. Thats too many double letters for me.
I also met a Brieanna. It seemed contrived.
I think it's a pretty name. I pronounce it Bree-AN-ah. Bree-AH-nah is pretty also.
I think its more trendy than classic.