A counterpoint is that if the vertex data isn't static, interleaved attributes may increase the cost of uploads, as you'll effectively have to upload all of the attributes even if only some of them were modified.

A related issue is that manipulating vertex data on the CPU will typically have worse locality with interleaved attributes because iterating over the vertices will end up reading and caching all of the attributes, not just the ones which are actually used.

But for static data, interleaved attributes will typically be better (and at least no worse) than using a separate region for each attribute.