Merged with comparison mega-thread, if you want to find ones like this that is possible by clicking the blue link at the top of PD for Psychedelic Index, then go to either the mushrooms or LSD thread and find this one in the listing.
For some people shrooms
seem to produce bad trips easier, apparently that is because LSD is more lucid and rational instead of dreamy. Mushrooms can guide by very deep feelings / intense complex interaction of emotion... and not everyone is connected to those as well. It can make things more uncontrollable or at least appear that way. If you believe that you have no control over your own mind and the things that manifest in them, well than that futility by default becomes true. Control is a funny thing though because to get it you might have to surrender to it all first in order to become synchronized with deeper parts of yourself or at least that is how I feel it.
Others may have very good intuition and may not handle the intense complex trains of thought with acid as easily, it can be more clearheaded but also more clinical. Not cold per se but rather transparent, without a definite own character. As if it amplifies less selectively. People who rely more on their instincts and natural feelings can possibly become bewildered more easily by the analytical effects of the LSD. I cannot explain a whole lot about that and solving the issue because it comes so natural for me. I find mushrooms far more difficult and am a pretty rational person.
I don't want to tell this as established fact though, I am not sure how people would agree with me here... but I certainly have noticed that some are like me and some are the other way around... and the explanation above is the best I have for what I've seen in these years.