I worked my way backwards through some articles by Evans to his published dissertation. I’ll need to do further reading from adherents to these different positions in order to really evaluate Evans’s presentations.
Evans, William B. “Three Current Reformed Models of Union With Christ,” Prebyterion 41, nos. 1-2 (Fall 2015): 12-30.
The three models that Evans notes are the “bifurcation model,” which he connects especially to Michael Horton and others at Westminster, CA; the “pneumatological-realism” model, which he connects to Geerhardus Vos and Richard Gaffin; and the “pneumatological-incarnational realism model,” which he connects with Calvin, John Williamson Nevin, the Southern Presbyterian John Adger, Thomas F. Torrance, and Robert Letham. It seems to me that Evans is least inclined toward the “bifurcation model” and is most inclined toward the “pnumatological-incarnational realism model.”
Evans, William B. “Dèjà Vu All Over Again? The Contemporary Reformed Soteriological Controversy in Historical Perspective,” Westminster Theological Journal 72, no. 1 (Spring 2010): 135ff.
This article also divides union with Christ views into three groups: (1) “Vos, Murray, Gaffin, et al”; (2) “The Revisionist Wing—Norman Shepherd and the Federal Vision,” (3) “The Repristinationist Wing—Westminster California.” The “Dèjà Vu” part of the title is due to similarities that Evans sees between these contemporary divisions and similar divisions in the 19th century. He thinks the Federal Vision and New England Theology are similar in their “repudiation of merit, and the foregrounding of sanctification,” though not in their ecclesiology. He thinks the Repristinationist Wing is similar to Hodge and the Princetonians because of their strong defense of federal theology, the ordo salutis, and the Law/Gospel distinction. He links the Vos, Murray, Gaffin group to Mercersberg, Shedd, and some Southern Presbyterians.
Evans, William B. Imputation and Impartation: Union with Christ in American Reformed Theology. Eugene, OR: Wipf & Stock, 2008.
This reworking of Evans’s dissertation looks at the theme of Union with Christ in Calvin and the Reformed Orthodox before turning to Edwards, the Edswardeans, Nevin and the Mercersburg School, and the Hodges at Princeton. He notes different ways that union of Christ has been related to other elements of soteriology and the impact those different configurations. The tone seemed rather negative, focusing on descriptions of how different configurations caused various theological problems. Noting such things is necessary, but I would have appreciated having this balanced out by noting the positives of each position culminating in a clear statement of the way forward.