This paper reports findings derived from a contrastive investigation of argumentative EL (English) essays composed by non-native university students with different cultural and educational backgrounds. While the texts under analysis here have not originally been intended for comparison and contrast, approaching them in this manner made a lot of sense when a general rating revealed that, overall, one group of students fared considerably better than the other in terms of negotiating the intended message and achieving their persuasive aim, despite their being at earlier stages in their EL acquisition. The investigation has been intended for diagnostic purposes and has therefore been targeted at three problem areas in which inter-group performance discrepancies were the most conspicuous: the ways in which text writers signal their intentions and engage with the reader, the level of commitment to the thesis they advocate for, and the kind of evidence they advance in order to support it.