Systematic cross-linguistic differences between alternative argument structure options are noticeable when contrasting English and Romance (Spanish). A good example comes from intransitive (unergative) variants, where a major asymmetry is determined by (systematic) vs. constrained productivity of monadic variants of causative-alternating verbs. The problem emerges more clearly when other, better-known forms of intransitive alternation (Property of Agent Alternation) are incorporated into the analysis. The distribution of these alternations reveals distinct well-defined verb sets with consistent semantic and syntactic behavior. Under this approach, we determine (i) the semantic (lexical) factors and necessary properties behind the grammatical patterns noted, (ii) the specific verbs allowed in each case, and (iii) their potential correlation to verb types classes commonly embraced in the literature. The paper fundamentally considers the correlation of these patterns with the Manner/Result Complementarity, the degree to which the verbs allowed or rejected in each (or both) intransitive alternations coincide with the complementary distribution often defended in the literature (Levin & Rappaport 2008, 2015), paying special attention to the verbs unexpectedly allowed in each case according to the usually assigned (manner/result) type. As a result, the intransitive construction alternatives analyzed here offer new and original evidence on the need to reclassify some verbs and/or the need of a finer-grained Manner/Result complementarity.