I went to the 3M certified installer in town- known for best quality around here- and they installed #25 all around on my 330ci. I like that set-up. Not too dark.
#25 is legal for front, #35 is legal for the back, in Florida.
I had the #25 installed in front on my 323i and #35 in rear and thought the #35 was too dark, so I was glad I had #25 installed all the way around on my 330ci.
They installed a sticker on the door jamb that states they are a certified installer and that the tint meets Florida code # XXX.