First of all, in my opinion, dark colored cars look better with the clear (aka Cobra, diamond corners) lights whereas light colored cars look better with the smoked lights. That's just what I think. My car << obviously is black and I've gone through 3 sets of Cobra headlights from 50resto, and 2 sets of diamond clears, and I just had yet another headlight problem. The innermost mounting tab just broke. Cheap junk. I'm honestly considering buying the good ol OEM Cobra headlights from Ford, with my discount I think they were right around $300 for the set, but at least I'll be getting good quality parts.
Personally, I think those one-piece lights (the black/clear in particular) look pretty cool IN THAT PICTURE, however, having never seen those lights actually on a Mustang I would be quite hesitant to order them. Because yes they may well end up making your Mustang look like a Hamster powered Honda or something. Plus when I had an Explorer I went through two pairs of euro clear tail lights from ProCarParts and they both leaked water.
I've just always had very bad experiences with aftermarket lights. I mean I understand they have to make them cheap to sell them cheap, as noone really WANTS to spend $300 or so on a set of headlights, but I'd rather pay more for good quality then have to deal with replacing them every few months.