Drug comparisons are tricky, because everyone reacts to them differently. Never take anyone's one experience with a drug as being your standard for what to expect. Nevertheless, I'll give a try at this, since I've used both...
First off, MDMA is in a class by itself in terms of pushing you into a positive headspace. I've yet to encounter another drug that requires so little effort on my part to stay optimistic, heh. It's not psychedelic at all in my experience; even when weed is thrown into the mix or I'm very tired, the experience becomes more delirious/dissociative than psychedelic.
2CB is a psychedelic in every sense of the word: you get visuals (watery rippling for me, usually, or pulsing/breathing effects), your thoughts meander along unfamiliar lines, and the power of your imagination is magnified to sometimes frightening proportions. 2CB, like most PEAs, has a nice body high to it; I personally get a "rushing" feeling, like standing in a strong breeze, and a sense of nervous excitement that can make it hard to sleep.
The only real similarity between MDMA and 2CB in my opinion is the feeling that most psychoactives give you: a sense of caprice, loosening of social inhibitions, and a nice body high.
The dosage is very, very different than MDMA. With MDMA, you have some margin of safety, since the dose is large -- on the order of 100-200mg -- and it's hard to put yourself in a bad place by taking too much (within reason, of course). With 2CB, you're talking about doses of 10-20mg; taking more than 40mg can easily put you in a very uncomfortable state of confusion. Most cheap digital scales can only measure within 0.01g, which gives a margin of error of +/-50mg...you can see the problem, I'm sure. 8)
If you've never done a psychedelic before, I recommend starting out with something a little less problematic, like mushrooms or LSD. If you have, I recommend using 2CB in a controlled setting your first few times, at least until you become acquainted with the effect that it has on you. Be careful, and invest in an accurate scale so that you don't end up in deep water.
