From second hand experience (I’ve never owned one but my cousin loves foldables), they’re probably more reliable than an unadorned iphone. Folding means the screen isn’t fully exposed.
The major advantage of the iPhone is that its ecosystem of cases means you can get some pretty high quality cases that can make it actually protected.
I really like my Surface Duo for exactly that reason, folding it hides the screens. The device dimensions definitely aren't for everyone, but having the option for a larger device and the usability of two screens really is pretty handy.
The Duo has its own faults though, the body around the charging port is particularly fragile due to how thin they made the device.
The major advantage of the iPhone is that its ecosystem of cases means you can get some pretty high quality cases that can make it actually protected.