Both are as valid as the other.
However, we're talking about one goal in favour, as opposed to three against, given the circumstances. Which had the bigger effect - the one about one goal, or the one about three?
In fairness I think had that pen/the chance afterwards gone in, the points were wrapped up - dodgy sub or not. I think the pen miss made W.Ham realise they weren't down and out and then the sub/tactics in that last 10 or so handed it them on a plate - combined with God awful defending from the players (e.g. Mori's attempted headers, McCarthy clearance, Barkley half-arsed attempt at a block and the poor tracking of Payet from Barry (who'd just come on mind) and Besic). Think some of that can be put down to fatigue but also general sloppiness which I won't pin all at RM's door - the players failed to prove they are as good as we all think they are as well as RM messing up.