Porous media air bearings distribute air more evenly. Because of this, they offer the benefit of more load capacity, higher stiffness, better gap stability, and more. Additionally, the porous material (graphite) has a natural lubricity. Therefore, your assembly will still work even if the bearing briefly makes contact with the guide. An orifice air bearing however, will have metal-on-metal contact which could damage both the bearing and the guide. The porous media air bearings won't get damaged from contact.