I have one of each, and I'm probably going to sell the triple stack and get another double.
It depends how you want to set it up though. My double pin I leave set at 25/40 yards (can shoot 50 aiming with the top of the bubble if I had to).
If I set the triple stack at 20/30/40, it would be just fine. But I don't need 3 pins to get out to 40 with my setup. With my first pin set on 25, I can aim dead on anywhere from 5 yards-25 yards (and I'm 2.5" low at 30). I can gap between 25 and 40 no issues.
So I set the pins at 25/40/50. This put the bottom pin really close to the bottom of the scope housing where the pin gets wider, and it makes it hard to see the target because this piece starts to cover it up:
So it really depends on how you want to set it up. I don't want or need 3 pins to get out to 40, and getting out to 50 puts the bottom pin in an undesirable location. So I can got to a 2 pin head and save a bit of weight.
If you want the ability to set your pin gaps, go with the triple stack. The double could possibly end up at oddball yardage like 20/37, or 20/42 or something like that which some people don't like.