-Has a nice Psychic and Electric typing to give it some nice STAB moves that cover most types.
- Has a good 95/110 SpA and Speed to make it a viable sweeper in game.
- Raichu gets good STAB moves in Thunderbolt and Psychic via Level Up and Evolution, but beyond that, you have to rely on TRs.
- Gets good Coverage moves in Surf, Focus Blast and Grass Knot.
- Has a Type Advantage against Nessa, a couple of Other Gym Pokémon and Leon's Charizard.
-Poor Defense and HP give it poor Physical Bulk.
-It overall has a Shallow Level up Movepool which makes you rely on TRs which may be time consuming.
- Even its Movepool with TRs is still lacking in a way.
- Its Lackluster ability leaves something to be desired during in game purposes.
- It struggles against many Gyms like Piers and Marnie.
-Bug/Electric typing gives it only 2 Weaknesses, Fire and Rock. Only Fire is majorly present in Shield.
-Levitate allows for nice Switch in Opportunities if needed.
- Great 145 Special Attack Stat. This gives many great opportunities if you over level.
- Has decent bulk, nothing extraordinary, but enough to last.
- Access to reliable STAB moves in Bug Buzz and Thundebolt.
- Has good coverage moves in Flash Cannon, Energy Ball and Air Slash.
- Is obtainable earlier than Pikachu.
- Has a Type Advantage against Milo, Nessa, Marnie, Piers and a few others, but also Charizard.
-Has a Horrible Speed Stat in 45. Although this can be managed by Agility, this is still bad.
- Vikavolt again suffers from a very shallow Level.Up movepool like Raichu, but I believe it to be slightly better.
- Even for its Type Advantages, it suffers against foes like Kabu and Leon's Charizard because of its slowness.
Conclusion: In the end, both Pokémon have mostly the same pros and cons. The only difference being their stats and abilities. Vikavolt's has much more utility in game, but its low speed is still a problem. So, it mostly comes down to what you want. I would say that Vikavolt provides better utility in game. Its STAB's cover many types and its coverage moves help it as well. Make sure to Level it up in Case of Charizard though.
Hope this helps!