Abbreviate Method of Agreement to MoA, Method of Difference to MoD, Joint Method to JM, Necessary Conditions to NC, and Sufficient Conditions to SC.
Source: p 552, A Concise Introduction to Logic (12 Ed, 2014) by Patrick Hurley
[...] However, when any of these methods is used as a basis for a subsequent inductive generalization, the strength of the conclusion is proportional to the number of occurrences that are included. Thus, an application of the method of agreement that included, say, one hundred occurrences might offer stronger results than an application of the joint method that included, say, only six occurrences. By similar reasoning, multiple applications of the method of difference might offer stronger results than a single application of the joint method. [...]
To minimise post length, I have not quoted this textbook's (confusing) definitions of the Methods.
Suppose that more occurrences exist for MoA and MoD than for JM. How do multiple applications of MoA and MoD overpower JM? JM reveals both the NCs and SCs.
Same question as 1, but now suppose the same quantity of occurrences for all 3 Methods.