I've had the 6120i for several years and love it.
I've been in a lot of shacks, and everytime I'm using it, or in a different one like the 9416 I like it even more. The round shape is way sturdier against winds and gives way more space. We setup a small table in the middle, drill holes in the corners (4-6), have a big buddy heater on one side, and have the chairs all facing inward (usually 4 adults). We stick the fish rods inbetween the frame poles and material so there's nothing to trip over with kids in there too. Usually have an underwater camera and/ or a flasher in there too, tackle boxes, food, drinks, etc. no problem. The doors are a bit smaller as mentioned otherwise its been so awesome to have. I've used it for a warm up shelter when bringing a big group of kids fishing, just with a buddy heater and a couple holes on one side with underwater camera and can fit a good dozen in there.