Even though Extreme Speed and Bullet Punch have the same power, I think Extreme Speed is better than Bullet Punch in almost every way. Bullet Punch is resisted by so many common types (Fire, Water, Electric, and Steel) and 2 of the 3 things it can hit super effectively (Rock and Ice) are raped by Close Combat so why would you even bother with Bullet Punch there. The only notable threats where Bullet Punch is better than Extreme Speed or Close Combat are Mega Gengar (banned) Scarf Terrakion (rare nowadays), Frosglass (will this thing even make OU), Togekiss (still not that common), and maybe a few other Fairys (who in general have higher special defense than defense and will probably fall to a +2 Close Combat or just get plainly KOed anyways). On the other hand Extreme Speed (especially at +2) can take down things that would stop Lucario's sweep such as Talonflame, Keldeo (scarfed), Jolteon, Mega Manetric, Greninja, Crawdaunt, Thundurus-T (scarfed), Starmie, Entei (if it's running Extreme Speed and it becomes popular), Whimiscott (Prankster will allow it to go before Bullet Punch and paralyze you), and many more if you choose to run an adamant nature over a jolly nature.
Also I would advise running this alongside Crunch and not Ice Punch so you can KO ghosts who try to switch into Extreme Speed and have perfect coverage in general. If you choose to run Ice Punch over Crunch I would still suggest this over Bullet Punch anyways for the reasons above,
Honestly the only reason people are running Bullet Punch is to "take advantage" of Adaptability...