You can see through dark smoke in the day time, but not well at night. If you have a dark smoke visor on your lid, it makes it tough to see through a dark smoke windscreen in the day. I'd say go with dark smoke unless you do serious night racing, which begs the question of why would you be going so fast at night....all tucked down like that. Plus it's not hard to just peek over it. I guess if you're a little guy you can fit under there easy though. 
Dark smoke looks better IMO anyways. I'd say go with it.
ZX6R_rider: i had the same predicament regarding smoked versus dark and i ended up blending the 2 that gave me some shielding around the clocks for the dark aspect plus the sides match in nicely to the fairing and the smoke in the middle to see through
Dont ask me what make as i have no idea i picked it up on ebay and havent seen any like it since, the dark is actually part of the screen rather than someone having stuck it on the back (like the backing on car windscreens)
I love the screen and wouldnt have it any other way. you may be able to search on the net for them.
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