[mangoandmimi]

The continuous floor space is more common sense than anything. It's the difference between a large open room and a series of corridors and small rooms, clearly the first is a nicer environment than the second and allows you to add proper enrichment. It allows for activities such as running - not achievable over a length of 30cm, and digging horizontal burrows among other things.

I don't suggest trying to justify that either of the cages you currently have are suitable even for a lazy hamster as that isn't the case. A cage approx 80x50cm is about the smallest you would want to go in my opinion. Would that fit? It's much smaller than the large eco habitat as that is quite a bulky and large cage I agree.