Go for the uniform 35% tint all around. It looks cleaner and IMO 20% on the rear is not worth the extra trouble of trying to back out of dimly lit parking lots at night. I know we have back up cameras but you have people briskly walking past your car thinking you automatically see them when backing up. Better safe then sorry. Not to mention the driver behind you can still see you so when they tailgate you I like to give a disapproving finger nod. It actually works wonders. 90% of the tailgaters will back off.

 

I did 30% all around and it's perfect IMHO... dark enough in the day, and still easy to see thru at night

 

My White TL and my BS G37 are both 20% on the back window and 35% on the other 6. I've always liked that look.