It isn't even a fight. Eelektross, of course. Eelektross is better than even Klinklang, let alone Klang.
In-game, Eelektross is a bit difficult to take down because he has no weaknesses and isn't very weak defensively. Its movepool is also the best among the new Unova Electric-types.
Eelektross can be compared to Galvantula, and favorably. After using both (Eelektross in Black and Galvantula in Black 2), I found that Galvantula absolutely must have Compoundeyes and Thunder to do any sort of damage, because its attacking stats are mediocre. It also dies very easily to neutral attacks. Eelektross, on the other hand, is reasonably balanced (apart from Speed) and learns a variety of good moves that allow him pretty good coverage. It's slow, and mine was the absolutely slowest possible (Quiet nature with 0 IVs), but it was still very dependable.
Eelektross also compares favorably against Zebstrika. The zebra is faster, but has paper-thin defenses and all of its strong moves (Wild Charge, Thrash) are too risky to use on a consistent basis. It's a good early game Pokémon but, like Luxray in Platinum, it suffers from a lack of strong dependable moves late-game.
Note that competitive tiers don't necessarily apply for in-game. Heck, in-game Arcanine is king, with high stats and wide coverage, but competitively it's only UU. Klinklang is RU, while Eelektross is NU, but Klinklang, despite having access to Shift Gear, doesn't have a wide enough coverage to warrant usability, unlike Eelektross.