Like anything else, you get what you pay for. You pay fifty bucks for a chip with a dozen or so mems, you're gonna know it, feel it. You won't remember that piss-in-your-pants fear as you free fall thousands of feet, you won't feel the snap of the cord or the sharp but wonderful pain as you're spared an embarrassing death.
Some writers are good, some writers are bad. Some MEMs are purely textual, like the majority of Daphne Mitchell's stuff; some rely on text, images, sound, and video to heighten the experience. Although it hasn't been determined whether these multi-sensory MEMs give better memories, it's safe to say that the more you pay, the better the experience.