If anyone tells you that one method is all sufficient, be wary.  A wiser approach is to understand the merits of differing systems.  This allows you to adapt and choose what works best given your individual skill set, your physical limitations, the particular situation, and the outcome you desire.  For instance, learning how to work firearms is one skill.  However, not all situations are best resolved with bullets.  Why not practice using situational awareness and threat detection to avoid dangerous situations altogether?  How about using body language or your voice to deter a threat?  Also, perhaps one shooting stance has merit in certain situations, while another might be superior in another based on ground terrain, distance, sympathetic nervous response.  Firearm training is only one tool in your tool belt.  To solve all situations with deadly force is myopic and a liability.

Additionally, there are many “internet warriors” and “arm-chair quarterbacks.”  These folks have strong opinions about what they would do in given situations, but they remain untried.  Many of these shooters and teachers have bad habits that those in the industry calls, “Training scars.”   One must test combative skills, and vet them by applying appropriate stress.  This is called “Forging” – pressure is added, and what works and doesn’t work becomes self-evident.  Heat is applied.  Dross is removed from the gold, and what is left is pure.  Never become so attached to dogma that you fail to recognize more efficient solutions.