Reusing previous review for similar paper Some months ago, I reviewed a paper for a conference (with a joint submission to a journal). I rejected the paper with a list of points that were missing and suggestions for improving the manuscript.

Lately, I have been asked by the same journal to review a paper by the same group of authors. Note that this is not technically a re-submission, as the title is different. In the new paper (which is about the same topic as the previous one), the authors have added a substantial amount of new material and have taken into account some of my previous suggestions; yet, I believe that many of the main points I raised in the previous review are still valid.

Thus, I am tempted to repeat verbatim large parts of my previous observations. On the one hand, these are still valid, but on the other, I am not entirely comfortable with this form of self-plagiarism. It will be very obvious that I have simply reused my own previous work, also because the Associate Editor is still the same and because I have my own default format for reviews.

A related issue is that in this case the outcome could be different: given the quality of the material that has been added, I am tempted to ask for major revisions instead of voting to reject the paper.

What is the professional conduct in this case?
Open your review with something along the lines of: 

I reviewed an earlier version of this work (entitled previous_title), which was submitted to conference_name. The authors have since added a substantial amount of new material and have taken into account some of my previous suggestions. However, many of the issues I previously raised have not been addressed. What follows repeats much of what appeared in my earlier review.

In addition (and if appropriate), you might like to add something along the following lines: If the authors address the issues that I have previously raised, then I'll consider the new material in more detail. As it stands, I consider the previously identified issues sufficient to recommend rejection.