I have an Ender 5-pro and when printing ABS and set the bed temperature to 110 the magnetic bed cover warps badly, so I bought another one with same result. They are from Creality.
The bed warps without any object on it ? 
Cause if it warps during printing, that’s not because of the bed. That’s because you have a good adhesion print/bed and thus the bed follows the warping print 
You probably right and I may buy the builtak because is metal and I have in other printer and works fine.