this is a remix from printables 

Ergonomics: One drawback of the original, though, is that it takes a bit of trigger force to launch a disc, and it can get a little uncomfortable pulling on the trigger. So instead of pulling the fork back around the disc with an index finger trigger, this design pushes the disc forward through the fork with a thumb actuated trigger from behind, which is much easier to do. The resulting design is odd, but comfortable to hold and use.

Performance: After completing my design, the first thing I noticed, rather unexpectedly, was that the discs flew a noticeably faster and farther than the original. Analyzing video of both versions, Uhltimate's design had a disc velocity of 20m/s, whereas my design came in at 28m/s -- a 40% increase. I also measured flight distances for mine of up to 15m. 

I think the biggest factor might be in different dynamics of the two versions. In the original, as the disc is being accelerated forward, the reaction force is pushing back on a movable fork, which has relatively little mass. So some percentage of the energy is going into accelerating the fork backwards. In my design, however, the fork is rigidly attached to the shooter body (and your hand) which are relatively massive, and hence, very little energy is lost in the recoil. (It's a conservation of momentum/energy thing.)

The other factor I can think of is that in the original design, during the acceleration phase, the disc has a whole stack of other discs being pressed down on it, creating a bit of drag. In my design, the disc has mostly exited the shooter during the acceleration phase, allowing it to be launched unencumbered.

Aesthetics: Well, the original looks like some sort of retro sci-fi weapon, where as mine looks like a water tower with a handle. I tried to emulate some of Uhltimate's design cues, but no doubt, the original is cooler looking.