I took MELAB on 20th of Feb, now I have experienced all the three tests lol, in my own experience, I believe the three exams are in general comparable, but I found out the speaking part in the MELAB is easier, while the vocabulary part was a bit tougher, writing parts are all similar in the three tests but I think MELAB evaluation for the writing was a bit tough, I got the right score at the end, but I have been living and studying in England and Canada for the past 4 years anyway and I got 8 in IELTS and only 87 but I guess this will also depend on luck.
good luck.