It's possible the two LED's are not the same, hence one is bright and one is dim.
If they were the same and if the wiring was wrong to one socket, I'd expect one LED to light and the other to not light, since they are light emitting "diodes" and diodes prevent current flow in one direction through them and allow it the other way. However, if it were me, I'd pull the fixture off the ceiling and verify that the positive wire (which should be from the switch) is wired to the same pins on both sockets. That would take the wiring out of the picture and point to an issue with the LEDs.
One LED might be "bad," i.e., made incorrectly. If you have another 1096 equivalent LED, I'd swap them around and see what happens.
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