The Zoom Fly Flyknit is definitely more of a longer-distance shoe. The Floatride Run Fast and Razor 3 are pretty comparable. I think both are great options for faster training or road races. The Reebok has been my fast-day shoe for the past 4 months, and I just got the Skechers out for a first workout today. The Reebok is more supportive and has a more traditional heel drop, whereas the Skechers is lower drop, and doesn't have a firm rim restricting side-to-side movement. This can cause a bit of irritation. The Reebok is a little heavier, but has a more grippy outsole. The Reebok is more snappy, but the Skechers is more flexible. The Skechers feels more cushioned under the forefoot and midfoot, but the Reebok might win in the heel. Either way, neither feel slappy at all for their weight, and I think both are great options. The outsole of the Reebok would make it better than the Skechers on trails, grass, and the track. It is probably a bit more versatile because of that.
Honestly, I think these are the two best lightweight fast-day shoes out there and you won't go wrong with either.
Floatride Run Fast:
+Better for varied surfaces and traction
+More heel cushion
+Snappier
+Better Looking
+Fast and light with a protected and responsive ride
-The EVA rim makes the shoe snappy, but goes a little overboard. I would reduce the rim so that it doesn't ever rub and cause irritation, and this would probably save the shoe some more weight.
Go Run Razor 3:
+More natural & flexible
+More forefoot/midfoot cushion
+Fast and light with a protected and responsive ride
+No rubbing from the upper
+Lighter than the Reebok
-Not as versatile for multiple surfaces
-Looks like hot garbage