They have extremely similar stats, but Electabuzz has a higher special attack and speed and slightly more defenses. Their movepools are also similar, but Electabuzz can learn Psychic, Fire Punch, and Ice Punch by TM, while Raichu cannot. They can both learn 2 HMs, Strength and Flash. However, neither can be obtained until after you beat the Elite 4 and get access to the rest of Kanto. If you want an Electric-type for the Johto storyline, you can get Magnemite on Routes 38 and 39, Voltorb by trading a Krabby in Olivine City, Chinchou by fishing with a Good Rod in the Olivine City Harbor, and Jolteon by evolving Eevee. If you want to wait until Kanto to get an Electric-type or if you manage to get an Electabuzz or Pikachu before the Elite 4, then Electabuzz has a better movepool and stats.