I thought you might just not understand the game well when you suggested that he should use Hypergrav over EMD, but now I'm thinking you might be trolling.
... Nobody thinks hypergrav is good until they play against my Captain America team and can't block the incoming mixup because the timing to block the crossup is nowhere near what it looks like. Then they lose a character because Captain herp-derps with insane damage.
EMD is good for a lot of characters. Wesker, Dante, Vergil, Dorm. Characters that have fast left/right crossups or can use it to extend OTG combos. It's not ideal for characters that already have strong zoning (Task) or... well Sentinel. What's he going to use it for? It doesn't help combo extensions. It doesn't help him get in (hard for him to combo off of because of slow normals unless he preemptively assumes he's getting a hit). It doesn't help with command grab mixups. It IS fast which helps Sent zone since high/low spit are slow AND it's useful for knocking people out of their moves when they try to challenge the machine, but other than that it's not very helpful.
There was another high level player that was talking about using Hypergrav with Sentinel, but it was on UMvC3 General Discussion or something on SRK and it got buried in there somewhere. Hypergrav assist is really good. It's better if you have a character with strong movement options or left/right teleport-esque moves (Captain backflip; Frank West roll; etc.). Hypergrav assist puts opponents in capture state and pulls them too you. This goes on for a good number of frames so even if you lose to a move with crumple or hard knockdown properties, chances are they'll still be in capture state while you're vulnerable for a combo. Hypergrav scales very little (I've heard rumor that it doesn't scale at all, but I haven't tested it out). And unlike when Magneto's a point character, it tracks even behind him. When it captures the opponent, it'll pull them to you for a large amount of frames so unless you're Modok sitting on the top opposite corner of the screen, you probably get a combo out of it. It's particularly good against opponents who like to teleport or come at you from weird angles.
For Task/Sent/Mags (for example) you don't need EMD.
If Sent is ever out there, you have spit (horizontal control) and Task assist diag/vert arrows (vert control). Yeah you CAN throw EMD out there, but what does it help you do? Shitty zoning? You're more likely to get Mags blown up. Yes he can also get blown up during hypergrav assist, but you're not likely to both be lined up like sitting ducks if you are using hypergrav assist (unless you're just terrible at calling it).
If Task is ever out there, you have drones for hori control and diagonal arrows for vertical control. Task doesn't really need EMD. I don't think he can use hypergrav assist effectively either, but it's not really for him. He may be able to do a combo into tk otg arrows into hypergrav -> sword sting.
