It's really a toss-up, for a first visit. You'll likely want to visit both places for something... Gatlinburg's shops, aquarium, pedestrian areas & the Nat'l Park... Dollywood, water parks, shows and outlet shopping in Pigeon Forge. So either way, you may need to brave the traffic (do ask at your lodging for a good roadmap with back roads and directions). The only advantage to staying in Gatlinburg is found if your lodging is actually within walking distance of the downtown area, IMHO.
If you want to stay in a nice cabin, see what's available to suit your needs and don't worry too much about which town is closer. We love staying at a nice resort in Sevierville, just past Pigeon Forge. Having a nice place to stay is worth a little drive away from the congestion for us. But we've been to the area several times now. HTH.