Hi Stephen
A question with an almost identical title except with no inclusion of the NEBOSH option was asked on 18 March 2024 on the Members' Forums, so here is a cut and paste of my answer then, but with a few more words at the end to cover the NEBOSH Diploma.
Usually on these Forums the discussion is about comparing a NEBOSH Diploma with an NVQ.
The IOSH Level 6 Diploma is fresh out of the oven and I don't know of anyone who has signed up - until very recently there was only one provider - IOSH itself though a second apparently with bases in India and the Middle East is now an approved provider.
Before the launch of the Level 6 Diploma, IOSH had a Level 3 Certificate but that appears to have been very quietly withdrawn from the market and IOSH has provided very little information as to how many people successfully completed it. That this product appears to have been a white elephant doesn't bode well in my view for how successful this new Level 6 Diploma.
Now it seems that IOSH is launching a replacement Level 3 Certificate, and is currently looking for people to provide it. Whether or not that proves to be more in demand that the previous Level 3 product, we wait to see.
In contrast, NVQs at what is now EQF Level 6 for those wanting to take the next step in their academic development as OSH professionals have been on the market for decades. Tried and tested.
In terms of the comparison you ask about, it seems to me that the answer is easy. Why decide to be a guinea pig whilst IOSH sorts out whatever teething troubles will go with its Level 6 product?
Plenty of threads on these Forums discussing which NVQ providers to consider.
The NEBOSH Diploma is also tried and tested, actually even more so than the NVQ option.
I am retired and my day job now is to mentor people at various stages of their careers a H&S professionals or seeking to break into the profession.
One of the questions that some of my mentees ask me regularly is which next qualification will be best for them. So, these days, we tend to discuss the pros and cons of NEBOSH v NVQ.
In simple terms NEBOSH is good for those who like exams and covering the theoretical.
NVQ is good for those who want to align their qualification to their own work (or perhaps that in some future role) as it is about putting together a portfolio, most of which can use actual outputs of the person's daily work.
However, it does require that their employer gives them a sufficient range of work opportunities to meet the various criteria demanded for an NVQ.
This does mean that the employer must be prepared to let the employee stretch themselves whilst making sure that contingencies are in place when the learner makes mistakes, BUT any sensible employer should be doing this as a normal part of the staff development, whatever a person's discipline.