It's simple and said before in other words, they might be similar but not the same. 2C-E has some really different tricks up its sleeves than 2C-B and can go miles deep and be serious and majestic while another 2C-X might be much smoother and more relaxing or be very rich and have more tendency towards the synaesthetic.
So the reason would be similar to why you tried 2C-B in the first place. If you can't figure out why you did that, then WTF. If you can, then it shouldn't be that hard to answer your own question.
Nobody here should push or pull you across the line, and let's not make this into a disguised 'what should I take?' thread. It's starting to seem like: "I tried 2C-B, what now?", in any case the answer to that is check erowid and take your time, check our Psychedelic Index and take your time. Read read read and read some more. If it doesn't interest you, then fine end of story. If something does interest you, track down more info and participate in our wide variety of threads.