As most members stated, the visual impact between single and dual frame is hardly noticeable. Instead, focus more on the profile of the mask. Lower profile means less gap between the eyes and the lens which will provide much accurate visuals and wider viewing angle. It will also be easier to equalize and purge water from your mask.
One of the main reasons for dual frame is the consideration of prescription lenses. Often times, manufacturers provide it for dual frame masks as the the correction for both eyes may vary. That being said, it's also understandable that the lenses from dual frame may be replaced while single frame usually can't.
I personally prefer a black rubber mask in comparison with translucent ones. Apart from what being said at previous posts, translucent masks are more prone to tunnel vision. Specially after a night of drinking before the morning dive

. They will also turn yellowish as it ages.
Most importantly though, the mask must fit your facial structure with minimal water sipping in and it's comfortable to wear.
Edit : Anyone going ADEX this weekend ?