I had a triple stack, but switched back to a spot hog double pin.
If you want 20/30/40, the triples stack is awesome. But for me, I use the double pin set at 25/40, and shoot the top pin inside of 30 in a hunting situation. So for me, the 3rd pin was kind of pointless if I set it 20/30/40, since I can get out to 40 without dialing with 2 pins.
I tried to set the triplestack 25/40/50, but then I had to run the bottom pin so close to the bottom, it was where the pins widen out and it blocked too much of the target for my liking at longer range.
With the double pin, I can aim with the intersection of the pin and top of the level at my home position, and it's on at 50.
I also really prefer having my top in the exact center of the housing. Makes it easier for me to center housing in the peep, and then the pin is automatically centered. To do this with the triplestack, you're limiting the space for the 2nd and 3rd pin, so again you might as well just have 2.
The MRT ring on the 2 pin head is the same diameter as the small MRT ring with the triplestack, so you run into fletching clearance issues at the same time. The single ring is smaller on the 2 pin head, so you could squeeze out about another 10 yards of max range by swapping rings.
I haven't had a dual trac, but the main benefit it has over the 2 pin spot hogg is you can adjust the distance between the pins.
After owning a landslyde, I've come to the conclusion that I really prefer the tape on the wheel, instead of a vertical tape like the black gold, so I won't be getting a dual trac for that reason.