The Gremlin is sort of like a Buzzz, but with less glide. Stability is about the same or it may be a tad less stable. I had it in my bag for a while, but I replaced it with a Buzzz. Don't know anything about the other disc.
I have a SL Gremlin from Discamania and am quite fond of it. In fact, just nailed an ace with it the other week. I have tried many mid-ranges and all I have found to be too under-stable for my likings. The Gremlin definitely does not fall into that category.
First released as Ching Sniper, Gremlin is the same as the second version of the Sniper. Sniper first came out in 1998, but it was not approved under the name Gremlin until 2007 06 05 after PDGA changed the rules. Abbreviation mark on the bottom = GR. GM (Greater Midrange) is made from the Innova Gremlin L-mold, a beadless Gremlin. This disc falls between a mid range and fairway driver with a speed between 5 and 6, glide of 5, turn of 0 and fade of 1. Abbreviation mark on the bottom = D-GM.
I like the Gremlin, I have it in the D and S plastics and there is a huge difference in stability between the two. The D I have has a decent amount of glide and is pretty controllable. The S version doesn't have as much glide and a lot more fade.
The DD I've never thrown but there is a long thread on it at discgolfreview.com. This disc hasn't been getting love like the other Discmania discs. I hear that it doesn't have much glide and that it isn't a real pure distance drive...more that it is good for a headwind.