Gladhill is very good, Burt Gold was my 1st instructor about 20 years ago.
The thing about accredited training (training courses are accredited, not certified) is that they are all, every signle one, created to the exact same requirements, so the information is the same and the big difference is in the graphics and delivery style of the instructor.
I'm accepted by both IRCA and Exemplar Global as an instructor, I've delivered around 200 or so Lead Auditor courses of all types and my recommendation is to try to find a course that is being delivered by someone who has real world, hands on experience in the subject matter, which is not always the case these days.
A question is ....Why do you need to take a Lead Auditor course? More often that not a, Lead course is a waste of time and money for the person taking it unless it is an absolute requirement of the management system standard (which it isn't), is an absolute Accreditation Rule requirement in order for an organization to become certified by a CB, which may or may not be the case, or the individual taking the training will be doing or planning to do 3rd party CB audits such as I do well over 100 days a year.
Another question is....Why would you want to sit in a learning situation being instructed by someone who hasn't done it themselves or who lacks the level of experience to achieve that which they are instructing others to do?
You're fixing to spend a few thousand dollars ($$$$$) so be very sure what you do is worth the cost.