i find acid more intense in some ways. it's smoother as far as a body buzz for me, but both give me good visuals on relatively low doses (2g shrooms, hard to say with acid).
i've done both with and without weed, and i love them with weed
it intensifies and can change the experience, but also calms me at the same time. it has more of an effect as i start to come down, and can help bring me back up. a few times i smoked in the morning when i woke up, and it brought on incredibly trippy feelings, although i doubt i had any acid/boomers left in me.