That's why I said Pichu is low tier, while Elekid is mid tier, Pichu needs less in-game time for evolve, but needs more real-life time (for the thing of the Haircut Brothers, who can speed up a lot that evolution), Pichu can learn naturally Thunderbolt before, but Elekid is better than Pikachu, so, you may want to evolve it ASAP with the Thunderstone and just use the Thunderpunch TM on it, at the end, Electabuzz is better on Kanto, but both are useful there, too, but Raichu can be better for all Jotho on overall, without taking care if you evolve it ASAP, or you level up your Pikachu to LV26 for the natural Thunderbolt.
With that said, obviously Elekid is better option than Pichu, but Pichu is not that bad, either, both are kinda similar, and Elekid is mostly better for learn fast and naturally Thunderpunch, and for it's extra coverage move for Kanto (and Elite Four at some degree), while Raichu have decent coverage, too, but not that awesome as Electabuzz. Thunder Wave is useful for catching wild Pokémon, anyway.
I love Caterpie, he's a so adorable little bug! ♥ (Also, sorry for my English, I'm still learning it and I'm not a native speaker).