You’re using VBOs, so presumably you care about vertex cache coherence and are using indexed primitives ordered appropriately (for example, using this).
For a regular grid, unstripped QUADs vs. unstripped TRIs, seems QUADS would actually be a tiny bit better. TRIANGLES = 3 indices/tri, QUADS = 2 indicies/tri. However, in practice I’ve never been index list bandwidth limited, and ordered the same, you should get the same vertex cache performance, so probably doesn’t matter much. One related plus for QUADs – you can fit more triangles in a single batch using unsigned short indices (fast path), which may mean fewer batches.