From one of them...
I was a many-hour-to-solo student and I respect my FIs erring on the safe side. But in the end I had a confidential chat to the Club Chairmnan who passed it on to the CFI (rightly). Suddenly at my next lesson, there was the CFI, in an uncharacteristically pleasant mood. He took me out, polished a few things and the next lesson met me clutching a hand held (I should have known). Did my solo; reverted to old instructor who promptly would not send me solo again!. So at that point I changed back to the CFI and finished the licence in normal hours. I went on to more advanced types and flew OK (or as good as a weekender usually gets) and passed all my renewal tests without problems. Managed not to bend a plane since.
The problem with the first instructor was that he did not let me make mistakes. Every flight was railtrack perfect with him gently covering the controls, so I never really knew what I was doing - everything was perfect. In contrast, the CFI kept his hands on his lap, mouthing abuse while we bounced all over the sky. He would calmly sit while I nearly went inverted reading a map and then grab the controls at the last minute. I really now knew I was flying!
So it came down to style of instruction. I should have switched at 10 hours but as a student one does not know this. Also not helped by training in a complex airspace environment off a big airport but that gave me heaps of confidence for operating in other airspaces.