Rotom-W says hi. He has the same typing, Hydro Pump, Electric-moves, AND better stats overall. The only things he misses out on is Volt Absorb, but both of them already have a neutrality to Electric-type moves. Not to mention, Rotom-W has a even more useful immunity in Levitate, which reduces its number of weaknesses to a lone 2x weakness to Grass.
Also, I wonder why Lanturn was somewhat used in OU 4th Gen (http://smogon.com/dp/pokemon/lanturn
). Maybe because of its BoltBeam resist and its ability to almost counter Life Orb Starmie and Sub + Thunder Wave Jirachi? Well, you have Rotom-H for that: better defenses overall, better Special Attack, higher Speed, AND a BoltBeam resist, although Rotom-H will have to flee from Starmie. Heracross MAY be relied on to beat Starmie, unless Starmie is also carrying Psyshock.
Long story short, Rotom-W is be better than Lanturn when it comes to partners and even as a teammate. Give it some thought.