I've only ever seen Contrastive Analysis in the field of S.L.A., not in a more generalised term but it's quite a vague term that seems ideal to potentially apply to many more domains than just S.L.A. Comparative Syntax, however, is much more vague and open and generally deals with analyses of multiple languages and how features are distributed across them in either a diachronic, synchronic, ad-hoc or even just general terms. My own interpretations would probably jump to the field of S.L.A with Contrastive Analysis but be in a pretty vague area of ordinary syntax with the latter one. The latter one is just basically is what the sum of the individual words would indicate.
