You should definitely EV train your Pokemon for competitive battling. While it may seem to take long and it be pointless, it can boost two of your stats by at least 63 points each(at level 100), if you max out your stats, which can really make a difference. Also, EV training has an effect on your Pokemons stats, but you can really see a huge difference at atleast level 40-ish.
- Mega Pikazard X