Well first of all, if you're going Lucario, I would suggest Special, but oh well.
SCIZOR
This thing is a BAWS. Technician and a 130 attack stat destroys all. Plus Bullet Punch, and Swords Dance can make this thing unstoppable. Plus he has a ton of types that he is strong against, so on any OU team, Scizor will be a big help.
However, also in OU is Ninetales, which is more than capable of taking Scizor down. Plus Infernape on Scizor can be a hastle too!
Overall, a very good Pokemon!
LUCARIO
Man, I love this guy. He's just so awesome. He has the awesome dual-typing of Fighting-Steel, and a ton of moves that he can use to his advantage. In my opinion, Lucario is a special attacker, but there is nothing wrong with a physical. He can also be used as a weather counter with Blaze Kick for Abomasnow, T-Punch for Poletoad and E-Quake for Ninetales.
But like every Pokemon (apart from Arceus) Lucario has his flaws. Again, Infernape can be a big problem. He can outspeed Lucario and OHKO him with a Flare Blitz/Close Combat. Even a Mach Punch would do a lot of damage. Also, he has to watch out for Landorous who is one of Lucario's main rivals.
Conclusion:
I would definetly go for Scizor. Techinican is a BEAST ability, plus priority in Bullet Punch and access to Swords Dance.
KUNG-FU STANCE!!!
