Having looked online at the items the Otty mattress appears to have it’s springs protected by the foam around the outer edges. I would also imagine that the springs can be compressed more than other springs meaning that they don’t break when rolled.
I would also imagine that they are vacuum packed allowing the mattress to be rolled tightly into the box.
The Silentnight mattress is one sided so please bear this in mind as you are instantly limiting the lifetime of the mattress as you cannot flip it over. I would assume that the spring system in this mattress is different to the Otty mattress meaning that it needs to be flat like our own models.
This is all pure speculation on my part so my best advice would be to speak those companies direct to get their input on it.
I hope this has answered your queries fully but if you do have any further questions please don’t hesitate to contact me on 0161 437 4419.