I'm really not sure about Pichu (C), given that Thunderstone's source is a Trainer Rematch. Since Raichu doesn't get Fire/Ice Punch he doesn't have Electabuzz's better coverage so his moveset is basically very wonky (Thunderbolt/Iron Tail/DynamicPunch/Quick Attack?). Electabuzz learns Thunderbolt naturally at Lv47, which roughly puts you to somewhere in Kanto. While Raichu has a slight advantage in terms of STAB damage, Raichu basically loses once you enter Kanto. Add to that Electabuzz has much more reliable moves as coverage (Iron Tail's accuracy is bullshit and DynamicPunch is...), Raichu isn't really that hot imo. Both suck early on, Raichu has better STAB while Buzz has better coverage, but Kanto basically throws Raichu's advantage out of the window since Buzz is now the one with better STAB and he still has better coverage.