The relative difference is because people generally don't process their shrooms very well and they take much longer to digest (slower release over time) and also its very impossible to judge the potency of the shrooms beforehand (so most go on the safe side dosage); as a starter shrooms are more unpredictable than truffles.

I had the same argument with a friend who gave me a bit of LSD (total dosage unknown, it was edible) and I tried a few days ago, it was basically the same as good shrooms. In fact, I believe the dose was on the low side, it was faster to take action but the "core" experience was shorter and "lower" than just 15 grams of good truffles.

The only thing with LSD is that it takes longer to completely clear out of your system (because it is already extracted in pure form, while shrooms have to be digested/processed by your system in a less efficient/effective way) but I don't like that very much because you end up in this in-between state where you are clearly not high anymore but also restless with secondary effects that are not really cool/interesting.

In any case it would be rather surprising if it was different, because molecularly they are extremely close.