Never used the grounder. Love the room in the Penthouse--I can hunt with my 66" longbow with another person in the blind with me with a longbow. Obviously we have to pay attention, and only one shooter at a time, but it gives you an idea of the room.
One thing to consider--they change the design on these things. I've bought Penthouse blinds...3 different times, I think, and the design changed a little every time. The last one I got had an awful zipper that crapped out on me quick, but that was a few years ago so I figure that problem has been fixed. I just hung up some black material as a curtain at the door and forgot about it--works fine.
Chad