There are quite a few differences between a Certified and an Experienced trainer. An experienced trainer has had experience working in the industry with the technology that he is training you with. Whereas the Certified trainer has a certificate with competent authority (Microsoft or Oracle for example).
This does not mean that the Certified Trainer doesn’t know what he is teaching, he would be quite adept at teaching the programming language and dealing with any bugs, but the caveat is that he may not have experience writing code in the industry.
Experience counts for a lot, that’s why people ask for experience.
There are many idiosyncracies of a language, then there are requirements from clients that needs a special kind of algorithm for different technologies. Hence you need industry experience from your trainer.
Now, a certified trainer may have experience or may not, but an experienced trainer would have experience for sure, hence the name Experienced Trainer. Go for an experienced trainer when you are looking to get trained in any programming language.