The big question that I posed was : "What credit ought we to give to the practical wisdom and strategy of a ministry when evaluating its success?"
Or, perhaps a better way to think of the same issue and one which makes the answer easier: "Should the success of a particular ministry, even if cast in terms of numbers of converts, convince us that the methods used by that organisation were (a) strategically and practically wise and (b) godly and true."
And the answer must be no. There is no guarantee in Scripture about which ministries God will choose to work in. If anything, there seems to be a tendency for God to work through those who are weak and fallible over those who are strong and able. (Though I actually don't think we should make much (if anything) of this principle in application to our current question.)
In evaluation of the methods involved, I currently reckon that we ought not to evaluate the success of the method, but its fidelity to Scripture, application of wisdom and its capturing of something of the heart and mind of God. Of course something that God has chosen to bless may well draw our attention to it and lead us to examine its methods, but the success itself isn't the determiner.
This is because it is not people or human wisdom that changes hearts, but Holy Spirit wielding the Word of God regarding Christ. Theologically I cannot come up with a reason for a positive answer to the question posed. Have I missed something?
If not, then I think there are many consequences for how we go about our daily lives, and every habit that we have. Including for this post.
Finally, a couple of quotes from Carl Trueman's blog post. Muy bueno.
[N]ot reveling in smallness and irrelevance does not require that I necessarily regard increasing numerical and financial size as accurate gauges of fidelity and truth.
Much has rightly been made by Reformed people of the problem of an understanding of Christianity that is driven by pragmatism as exemplified by the Joel Osteen `be a Christian and be a better you' mentality; much criticism has also been lodged against the church growth movement because of its tendency (in the words of an old song) to find out what they like, and how they like it, and let them have it just that way. But the dangerous thing about pragmatism is that it does not necessarily reject the truth; it merely renders it subordinate to the desired end. To be precise, pragmatism evaluates means in terms of impact and results; and the implication of this is that even means that are intrinsically true can still be co-opted by pragmatism simply because they seem to be achieving the desired results at some particular point in time.