Bellow is documentation of my workflow from Substance Painter to Arnold based on what is posted on substance3d.com and classes taken at SCAD.
SUBSTANCE PAINTER MAP EXPORT
In Substance Painter, be sure that the PBR Metallic/Roughness Shader is being used. In this guide, I use the "Document channels + Normal + AO (No Alpha)" for the export configuration so that an ambient occlusion and scattering maps can be used. It is important to note that using this configuration will export the normal in the DirectX format (refer to the Normal Map section for setting the proper Arnold Attributes).
Export: Setup for each texture set and export the project as textures
Configuration: Setup for export presets. This tab does not need to be modified when exporting textures unless customizing a preset.
LIGHTING SETUP
With correctly exported PBR maps, materials should look correct in all lighting situations. However, to get a closer match to what is seen it Substance Painter, you should use the same environment map when rendering in Arnold.
AISTANDARD SURFACE SETUP
The following table shows the aiStandardSurface material inputs and the corresponding textures exported from Substance Painter.
Channel Setup
GAMMA SETTINGS
Make sure you have Color Management Enables. When importing a bitmap, the color space needs to be properly set. This can be done on the Color Space option of the file node. Maps that represent data will need to be set to RAW. Maps that are greyscale such as metallic and roughness will need to have "Alpha is Luminance" enabled.
USING A NORMAL MAP
The normal map is applied to the aiStandard Surface using the bump2D node by default. If using this method the bump2D node should be set to Tangent Space Normal. It is important to note that Maya works with OpenGL normal direction. Maps in Substance Painter will be exported as DirectX or OpenGL based on the project settings as well as the Export Settings. Maps exported from Substance painter using the Arnold 5 export preset will be converted to OpenGL. If using the "Document channels + Normal + AO (No Alpha)", the normal direction will be based on the project settings.
If the map is DirectX - Uncheck Flip R Channel
If the map is OpenGL - Uncheck Flip R Channel and Flip G Channel
Note: Using the aiNormal node does not utilize a bump2d node and so no channels needs to be flipped for the normal map to render properly. The pro of using the anNormal node versus a regular file node for the normal map is that there is the option to increase the intensity of the map directly.
WORKING WITH TRANSMISSION AND OPACITY
To correctly render transmission and opacity, the Opaque setting needs to be disabled on the Shape node of the geometry. If Opaque is enabled, opacity will not work at all. Transmission will work however any shadows cast by the object will be solid and not pick up the Transparent Color or density of the shader.
Any opacity maps exported from Substance painter should be plugged into the Geometry>Opacity input of the aiStandard Surface Shader. Colorspace shout be set to RAW and Alpha is Luminance enabled. Use Thin Walled if you are working with single-sided geometry.
A Note on Subsurface Scattering
It is important to note that value of SSS in Substance Painter is purely a preview in relation to how it will be implemented in Arnold. To get the full range of the map being created in Arnold, the SSS value slider will need to be set to a value of 1 in Substance. This may cause there to be more than the desired amount of SSS in the Substance viewport however it is the values greyscale map that is important. This can be controlled with a levels filter in Substance or with the exposure amount in the file node in Arnold. If the SSS amount is not at a full value of 1 in Substance when the maps are exported, the map will not contain enough information to properly display the SSS in Arnold.