Many people here will tell you that EPtS rules everything, always, because of the resistance bonus that it gives your shields. And in most cases, that is true, especially for escorts.
RSP is great even without TT (because of manual redistribution) for healing your shields, but once it wears off, the lack of shield resistances makes the just-healed shields go away pretty quickly. In a cruiser, you want to have both, two copies of EptS and RSP, but in an escort where you will, at most, have three slots for engineering abilities and too few sci abilities to give you extra shield healing, you are better off with EPTS, because your shields will last longer: Even EPTS1 gives 18% bonus damage resistance on top of what your (now boosted) shield energy level gives you. So, 1000 points of incoming damage become less than 820 points that way, to be further diminished by native shield resistances and shield energy level.
And you can have two copies of EPtS which basically keeps that up all the time, whereas RSP can be up for something like 10-15 seconds, and then be on cooldown for 45 seconds... in a game where an unprepared-for alpha strike will kill you within 3 seconds.