Umm, I have experience with IELTS and CELPIP. IELTS was much easier for me, I've got 8.0 average (out of 9) because interviewers are human and can give you a bit more time. I did it maybe 3 times before I got the score I needed. CELPIP on the other hand is heavily computerized and if you don't fit into 30 seconds - you're done. Even with a signed piece of paper from a doctor I didn't get the score I needed from CELPIP.