I think it depends on the person. Some people are better at exams, others coursework.
The idea that BTECs aren't academically rigorous is untrue, in my opinion. I did BTEC Music, and for each unit I had a log book to fill in weekly, at least one essay (sometimes two) and a performance of at LEAST 3 pieces, though sometimes more. The one exception was the music business unit, which was 3 essays and a presentation.
I also did a-level music though, which actually commanded less from me than the BTEC. An exam, which covered 3-4 topics, depending how you look at it, 2 compositions with a log, and a performance, but no programme notes or anything were needed for the a-level, I just played then left. The reason the a-level was challenging wasn't because it was 'harder' it's that it has everything at the end. If it was more spread out like the BTEC, I think I would have done better, because I actually preferred the a-level content. I got a Distinction in the BTEC and a B in the a-level.
I don't think there's anything wrong with doing BTECs, and I think they should be available in more subjects, like history and other humanities. I think the high content of coursework probably actually prepares better for uni in humanities and arts subjects. I know the unis I want to go to have mostly coursework assessment, with less exams.