I have the Matilda Rotating Mat I purchased it I believe on Black Friday from the Fat Quarter Shop at the time they had the best price + shipping I could find on the internet.
I also have the square olfa, which I have used for years, it is easy to pack and take to retreats or classes.
I also was able to find the Elna Amazing turntable via eBay and I really like it too for certain projects I'm working on.
I personally prefer the Matilda mat, in my experience have not found the Matilda to be prone to tipping. The ball bearings make the Matilda phenomenally easy to rotate and adjust to just the right/position or angle I need to cut, trim or square up.