I prefer NIC grids. They are more versatile. They can be put together into an open pen configuration that is similar to an x-pen, so anything you can do with an x-pen you can do with NIC grids, plus a million other things too.
Currently we have a three level condo with a large open “porch” area. The condo acts at his warren, and the porch area as he open space. The porch looks a lot like an x-pen, but is all NIC grids.
The porch panels are three grids talk, with a slight over lap of two squares so they are rigid, then they are attached with not over lap so they are flexible and can be set up in a curved configuration. I attached the porch to the front of his condo and just leave the condo door open so he can come and go as he pleases.
The condo is totally constructed from NIC grids as well. No cutting wood for the levels. I just covered the floors and ramps with carpet protector, cardboard and mats.
If you search the forum I have posted before extensively about Porky’s condo and then later about his porch when I added it.