Vikavolt was more usefull when I used it, and I think it will be for you too. Both Grubbin and Pichu come at the same time, but unlike Pichu, Grubbin doesn't require a friendship evolution, and has a typing that can help vs Hala.
Vikavolt has insanely high Special Attack which lets it deal great damage to mostly everything. Raichu may have the Speed advantage, (very clearly) but Vikavolt's power comes into handy more often. Plus, with a magnetic field at Blush Mountain, you get a nice full evolution time.