I would recommend the Harrison Pup if cost is not an issue.
I also have a Photoflex (very similar to the Calumet). Although it pops up very quickly, it has much less flat floor space than the Harrison - I found that the the floor curves up quite a distance from the edges.
It's amazing how much (flat) space you need - a stack of empty holders, a stack of full holders, an opened box, film and plastic liner. In that respect, the Harrison is a clear winner.
Merry Xmas,
Andrew