I have heard words to that effect from an elder during casual conversation. I believe such words reveal that deep down they do have doubts about the organization being the Truth and such reasoning is actually a rationalization for why one should remain.
But the statement is false. JWs don't live the best life. Shunning your own flesh and blood just because they leave your religion and join another, is not the best way of life. Refusing higher education and therefore hampering your ability to fulfill your full potential economically and societally, is not the best way of life. Refusing life-saving blood transfusion for your dying minor child or yourself, during a medical emergency, thereby consigning yourself or your child to almost certain death, is not the best way of life. Holding a prejudiced view of everyone around you, labelling them as "worldly", "bad association" and "unbelievers" just because they don't belong to your particular sect of a religion, is not the best way of life.
I can live a good life with the same moral standards as JWs, without drug abuse and the other social ills JWs prejudicially paint everyone as suffering from, all without having to practice the ills mentioned above that are specific to the JW way of life. Many non-JWs of other religions live that better way of life.
More importantly, we can use their own Bible to call them out on their best life BS! If they are true Christians as they claim then their way of life is definitely not enviable, according to the Bible. In 1 Corinthians 15 "Paul" says that Christians are to pitied more than all other men if Christ was not raised up! Why would he say a thing like that if the Christian way of life true was the best? His words reveal that the Christian way of life is one filled with trials and hardships. It is a difficult life that is to be endured only because of the hope of the resurrection and the promise of future eternal life. Not the best life - but a drudgery worth enduring to gain the prize of eternal life.
The JWs are lying against reality and against the Bible itself! Best
life lie ever!