Let's look at the pros and cons:
Luxray
Pros:
High 120 base Atk Stat
Easily accessible
Passable Defenses
Only one weakness
Cons:
Raichu:
Pros:
Cons:
So with those pros and cons in mind, I would probably do Luxray, but Raichu is still fine. If you are willing to wait, some other (better) Electric-types would be Electivire, Magnezone, and Rotom, which can all be found in the fourth area. Luckily though, Eevee can be found in the first area which can evolve into Jolteon. Hope I helped!