Stat-wise, Dracozolt and Arctozolt tie ahead of Toxtricity with a BST of 505, while Toxtricity only has 502. However, you can get a Toxel immediately after first badge, while the two fossils are a bit later on. If you are using it purely for in-game play, the 3 BST difference is not likely to make a huge impact on the playthrough. Plus, Toxtricity gets Overdrive and Boomburst, excellent moves further boosted by its ability, Punk Rock.
TL;DR: I would choose Toxtricity, as it can be found earlier and learn some pretty decent moves.
Hope I helped!