Well, at first glance I don't think the problem lies there: broadly speaking I know what ripple is, at least for linear technologies, while I don't know measuring techniques, particularly for SMPS.
I'm just wondering how different time window on the oscilloscope may affect a given output voltage and relevant artifacts, which should not change (or not that much) whatever you will do to measure them (on the oscilloscope settings, with reference to probes and ground loop I guess it would be another whole story: but as I said just above, I don't know measuring techniques/methodologies).