Justin Gravitte works for The Navigators and writes about the forms of discipling below.

One to one disciple making relationships are as small as they get. The size allows the leader to focus the meeting precisely where the disciple needs it. The goal is to help the disciple grow to maturity so that he can reproduce. Defenders of one-to-one will suggest that the focus and depth allows the disciple to grow quickly and holistically. They also point out that Jesus had an individual relationship with each of His disciples, not primarily a group relationship. Detractors argue that one to one discipling produces unhealthy dependence and puts too much burden on the discipler to be omni-competent.

Triads are groups of three (shocking, I know). Like micro-groups they commit to meeting together for a period of time. The smaller size allows the leader to go a bit deeper with each person. The goals are largely the same—accountability, growth, and multiplication. Triads are a bit less likely to use discipleship curriculum, though most do. The smaller size allows the leader to get more personal with each member. Defenders of triads will suggest that the size is big enough to allow those being discipled to learn from one another, but small enough to still be very transparent. Detractors argue that since no two people are in the same place spiritually, the triad forces a leader to use curriculum or to choose which person to focus the content on during meetings.

Micro-Groups are groups of 4-5 people who commit to walking together for a period of time to focus on growing in disciple making. A group of four is presented as the ideal to create an environment of accountability, transparency, and community. Micro-groups normally work through a discipleship curriculum together and upon completion each person is challenged to become the leader of a new micro-group. Defenders of micro-groups will suggest Jesus with Peter, James, and John as an example. Detractors argue that micro-groups function like just another small group. The problem can be that the disciples don’t get life on life time with the discipler.

So which form do I choose? Here's a few thoughts to consider:

First, aim to reproduce the depth of relationship Jesus had with His disciples. Jesus’ relationship with the disciples was individual, personal, and deep. The closeness of each relationship was vital to their development. We only get a glimpse of this, but imagine the conversation Jesus had with his men while they walked on the road or sat around a fire late into the night. Each man was deeply known by Jesus and experienced his love through that depth. Regardless of the form, our relationships with those we are discipling should be the same.

Second, don’t choose a form based primarily on its efficiency. Americans are infatuated with efficiency, but Jesus’ investment in twelve for around three years doesn’t indicate that He shares our desire to scale quickly. Yes, He was strategic and planned for the disciples to multiply, but He did it slowly (and after He was gone). He didn’t ask them to go find one, four, or twelve to disciple after just a year. If he had, there could have quickly been 144 and after another year 1,728. He invested in twelve men 24/7 for three years. Why do we think we can do the same in one year with much less investment?

Finally, train disciples of Jesus, not of a program or curriculum. Jesus’ men were fully equipped for the work of discipling by the Word of God (2 Tim. 3:17). Regardless of the form we use to make disciples, we must be careful to equip people to disciple others, not to simply lead others through a curriculum or program. The previous two points are relevant here as well. Investment must be done relationally and not based on how quickly we can get reach the masses with the vision of discipleship.