The problem with acid is that you believe everything you think, so be careful what you think :)
Aside from LSD's longer duration[^1] and increased potency[^2] acid also has a dopaminergic action, whereas psilocin[^3] is primarily a serotonergic drug. It is the dopaminergic action that can result in the obsessive quality or "looping" experience of LSD trips.
When you eat magic mushrooms, you are essentially taking yourself for an existential ride by voluntarily staring into the abyss. The trip itself is primarily "weird" and euphoric, but IME, what many people refer to as a "rough trip" is actually the existential rebound that begins 1.5-2 hours in. During this serotonin recoil, you can face the heart of darkness: the realization of all potential simultaneous chaos and creativity.
This state can include a ton of beauty, but also a reminder of your own inevitable demise. This visitation to a more "eternal" mode of thought has the same effect as surviving a face-off with any dangerous unknown: radical personal transformation. Self-knowledge necessarily feeds back into your world-view, thus changing you (usually for the better, but not always).
Nowadays, when I embark on a shroom trip, I do so in the knowledge that I will have to stare into the abyss. Sometimes you have to chew glass while doing so, e.g. a friend enters a psychotic state, or somebody dies and you have to be useful. Nevertheless, you become vulnerable and have the opportunity to learn something, help someone, or be helped and form new relationships.
Advice for brave mushroom eaters:
- be well-rested, preferably in nature
- don't trip alone, but keep it under 6 people
- have music, or an instrument nearby
- don't eat more than you can handle (0.7g is potent. 2.4g is effective. 4g is high. 10g is godlike and dangerous)
[^1]: LSD duration is 8-12 hours. Anything less than 8h is not LSD.
[^2]: psychoactive LSD dose is 25µg and up, hence LSD-25.
[^3]: the primary psychoactive metabolite of psilocybin