I used a light tint on mine. It's not a noticeable difference at night. I'd like to go darker, but I think I really woudn't be able to drive at night then.
I have a kit from xpel.com... you get what you pay for, $70 for heads, fogs, and turn signals, but the quality is noticeable, I mean it is made by 3M you know?
This is mine. I used film from Lamin-X. it works amazing, I can see just fine at night with my HID's. Not sure of visibility without HID's though. I have used this film on a few cars and it is a very good quality film.