The former. Don’t even worry about performance. CameraType and any other EnumItem property do not take arbitrary string values. CameraType is not a string value, but an EnumItem value. if you do typeof(camera.CameraType) you should get the latter in the output.
Technically doing it this way would be faster since there is no extra stuff going on to cast to an EnumItem.
Worth saying that regardless, the value you apply to a property that expects an EnumItem will convert itself if what you’re passing is valid. The string Plastic will be converted to Enum.Material.Plastic (which comes from the Name property of this EnumItem). Likewise, setting the Material to 256 is also valid because that’s the EnumItem’s value.
For your own sake and everyone else’s though, please use the full Enum over strings. It’s more clear what you’re doing and clarity is a gift.