Reformers, Romans, and Radicals

In his chapter on apostolicity in People and Place, Michael Horton seeks to demonstrate that the locus of ecclesiastical authority is not centered in one person or office, but that "both [Peter and Paul] subjected themselves jointly to the broader assembly [in Acts 15]," and that "if the apostles themselves were corrected by the Word, through mutual admonition, then surely the ordinary ministry can assume no greater authority." Horton then cites Calvin as pointing out that Paul, in his list of officer-gifts given to the church by the risen Christ, mysteriously leaves out the (supposedly) most important one of all:

If he knew a primacy which had a fixed residence, was it not his duty, for the benefit of the whole church, to exhibit one ministerial head placed over all the members, under whose goverment we are collected into one body?

Horton's larger aim to to demonstrate that a covenantal ecclesiology is a via media between a hierarchical model of apostolicity rooted in historical succession on the one hand, and a democratic model based on private revelations or inner experiences on the other.

In fact, argues Horton, the Reformers' argument in the sixteenth century was that both Rome and the Radical Anabaptists appealed to the ongoing revelatory ministry of the Spirit, they just diffeed in whether his voice was to be sought in the Magisterium or in the heart of every sincere believer.

The church is not, properly speaking, the magisterium or the ministerium, but the whole body. Yet as the Pastoral Epistles elaborate, the transferable aspects of the extraordinary apostolic vocation have been entrusted to the ordinary offices of pastors and elders. So we must avoid a legalism that subverts the unique authority of Christ and his Word by addition as well as an antinomian spirit of subtraction.

My question for my Catholic friends, then, is: If you can argue that there is no difference in principle between the Reformers and the Radicals since both reject the magisterium, can we not argue the opposite, namely, that due to their rejection of the sufficiency of Scripture, there is little difference in principle between the Radicals and Rome?