For me: LSD is like the walls of reality melting before your own eyes. Mushrooms is like you mind melted with a wild animal. DMT is like your consciousness melts with your imagination.
I agree w the above r.e. lsd/shrooms .. never done dmt tho.. not particularly interested. I've done salvia which I've been td is like a super light version of dmt, and was not a big fan.. thought at least salvia is only about 15 minutes :D lots of ominous dread.
On LSD I've always still been in the room, or at least had some idea of where I was. On DMT, I'm not even on the same planet and I don't remember where my body is.
It really depends on how much you do. On a sufficient dose of LSD or mushrooms, you can lose all connection with physical reality for (what seems like) eons, and "travel to" (or construct?) arbitrarily weird places. But for those substances, it may require more careful setup (quiet, dark room, eyeshades). With DMT you don't have much choice.