I'm more of the belief that Briggs went to the Black Lodge.

1. He returned with a tattoo. We only have heard tattoos mentioned with one character: BOB. One of the sprinklers that started to pour when BOB exited Leland also starts to drip water on the photograph of Briggs' tattoo, as if in warning.

2. He saw a disturbing vision of a giant owl. BOB was connected to the owls.

3. There's a flash of fire when Briggs recounts his tale. BOB was also linked to fire.

 I think that the White Lodge is Heaven. Each persons view of Heaven is different so Lynch was wary of showing it. He could also believe that it is so beautiful anything depicting it would fall far short. That said we did see a few glimpses of it via the Angels in FWWM.