I believe there is much difference, but really it is personal. I know folks who dont like mushrooms, but love trippin' on acid, and i know folks who dont like acid but love trippin' on shrooms, or people like myself that dont mind both I think its kinda hard to say what its like, its always been different for me, like a learning experience.... You just have to have a very open mind
I have pretty limited experience, I've only done mushrooms twice and LSD once. I have done LSA three times, and the LSD feel is certainly there, but of course it's a different drug. Both times I've done mushrooms, I've felt the same sort of mental highness. I know that I'm tripping when I'm on mushrooms, it was pretty in my face. There was more of a connection to everything (at least for me). Visuals were pretty intense and involved a lot of "swimming" and waving, and cartoon-like colors (vibrant). LSD was a lot different- it was almost like I was insane. I was, actually. I knew I was tripping, but I didn't "feel" quite so high- it's just like my thought pattern totally changed and when odd thoughts occured to me, they weren't "out of place" or anything- they were just a part of my mind at the time and that was that. Looking back I felt a lot different than normal (my body felt slow when I moved and sort of "trailed" behind me), but at the time it felt very natural. My visuals were more in the way of my mind; everything I saw sort of took a place in my head (during my peak, I looked around and everything took its own puzzle peice in my mind- I could see it very clearly, even physically, but it's really hard to explain. I also remember the world looking distinctly red). LSA was similar to acid in that my mind felt sped up, and I experienced this "logic web" where, instead of my logic going in a straight line like normal, there was an intricate web in my mind. I didn't get any visuals on LSA, though. I've learned a lot more on LSA than any of the others, but that could be because it's the only psychedelic I've done alone, which makes it more condusive to introspection. I'd suggest trying mushrooms first, only because it's easier (in my opinion) to get into- acid was just really weird, and I'm glad I had tried mushrooms before doing it. Also, if you haven't been to www.erowid.org yet, I'd strongly suggest looking at the experience reports for both mushrooms and LSD, they can give you a sense of what to expect.
ive had relatively mild trips with both, and would praise lsd highest. Mushrooms left me in a slighlty vegatative state where interacting with others was difficult. LSD opens not only your senses, but will tap directly to your thoughts. It can provide the best or worst trips immaginable, and for me, it was very good. but try em both
acid is better if you look at it in terms of potency. it's easy to have an adequate break -through dose, but with common shrooms you need to ingest a lot of material to achieve the same transcendent level. tea is always an option, but many say even that gives them a stomach-ache. L doesn't give you any physical stomachache, but your mind might create one to convince itself that it is still embodied. So I guess it depends on what you're expecting/hoping for. Low doses of shrooms (~1.5 grams) can be a lot of fun, but if you are more interested in a penetrating and possibly challenging psychological/spiritual affair, 3+ grams of shrooms'd be good or better yet, 2-3 doses of decent L.