A lot of people don't gain anything from doing *any* of these substances.
I suppose it is somewhat a matter of taste, as well as body chemistry, as well as set and setting.
The phenethylamines have a lot of different things to say than the tryptamines, I think.
What I found to be a really potent and eye-opening combination was MDMA and LSD. In the typical 'dance' setting, you can be mindless and just enjoy it, or you can remove the external stimuli and the information would just flood in.
I huess it's just me, but I have had mystical experiences with high doses of MDMA......but the whole character of the experience, even in the most intense parts, was a lot more relaxing and enjoyable to me. For a long time I loved that feeling of being on the 'Third Rail' with LSD, but it's something I enjoy in moderation these days. (my set and setting = no good right now)