Super Training is really just another form of EV training--Game Freak finally decided to let everyone officially know it was a thing with this.
But yeah, the traditional way of EV training (now made faster by horde battles) is still generally the best way to go--lot faster and a lot less effort. Super Training still has its uses though, like if you're going for something more specific than a standard 252/252/4 spread since you get much less EVs per Super Training exercise, which allows for some finer control in some cases.
Like let's say you're making something with a 252/32/220 spread. You're first wanna get that 32 EVs by doing 4 rounds of that stat's level 2 Super Training 4 times, since horde EV training only gives ~25 or 50 EVs per round, making it so you can't get 32 really. Though I suppose you could just get those 32 via single battles and not horde battles too lol.