How different is the Inferno's armor variant compared to the Ion variant?

The Inferno's armor will be significantly more effective and thicker. In the short term, before physicalized damage is introduced, this will come in the form of extra health, but once physicalized damage comes in the armor will be thicker and tougher to get through. The Ion has relatively thin armor due to other components taking up a roughly equal amount of mass, equalizing the flight performance of the two variants.