I can't help but think Red overlooked some key points so;
Lucario (Stats) - 70/110/70/115/90 (HP, Atk, Def, SpA, SpD, Spe)
Infernape (Stats) - 76/104/71/104/108 (Same format)
So as you can see, Lucario possesses higher attack and special attack, while Infernape posses the higher speed, and bulk by literally a tiny bit. No one cares about bulk since it's both so low anyway.
Both Pokemon retain excellent mixed attacking stats, with Lucario having higher offensive prowess and Infernape having better speed. Both Pokemon also have access to good movepools, both boasting moves such as Swords Dance, Nasty Plot and Close Combat. They both have priority options, with Infernape having Mach Punch and Lucario having the much stronger Extremespeed as well as Bullet Punch and Vacuum Wave. Also Infernape gets access to Stealth Rocks.
Typing-wise, Lucario with it's Steel/Fighting typing it gains a resistance to Stealth Rocks and an immunity to Toxic Spikes, something which Infernape cannot boast. Infernape's Fire/Fighting typing gives it access to an excellent stab option apart from Fighting, being Fire. Lucario also resists more types, giving it a little more switching in capabilities, as well as setting up capabilities.
Abilitywise, Lucario has Justified and Inner Focus while Infernape has Blaze and Iron Fist. Justified allows with smart playing, Lucario to gain a free boost if it switches in onto a Dark type attack, while Inner Focus prevents flinching. Iron Fist provides Infernape with an excellent ability, increasing the power of all of Infernape's punching moves. Blaze increases the power of Infernape's already powerful Fire STAB attacks at a low health.
Anyway, it's really hard to decide which is better, and it depends on your team as well. Obviously you don't want too many overlapping weaknesses and too little resistances in your team. So choose whatever suits your team more