These two Pokemon have their flaws and their pros. But overall, two decent Pokemon!
- Jolteon: One of the strongest Eeveeloutions, Jolteon makes an excellent special sweeper, with such great speed and special attack. A simple Discharge can almost take out anything in it's way.
However, if Jolteon wasn't in OU, this would make using it way easier. It has to look out for quite strong Ground-types, like Landorous, Hippowdon & Donphan. They are easily capable of taking Jolteon out very quickly. That is one of it's biggest flaws.
- Manectric: Another good choice for a special sweeper, but it does have almost IDENTICAL stats to Jolteon, but a whole lot weaker. It has a pretty easy time around, because there is there is only one threat to Manectric. Sandslash, Being one of the only Ground-types in RU. Manectric can hold it's ground against many other types. Although those poor defence stats are not doing anyone a favour!
The choice is up to you. But even though Jolteon is a lot stronger, I would suggest Manectric. It's decent speed and Sp.Attack are capable for sweeping, but you need the correct materials. Although there are far better Electric types than Manectric in RU, Like Rotom.