There are a few critical differences between BS and LZ that define BS as more "metal" than LZ. Bear in mind that I am a drummer, so I am partial to LZ (Bonham, God of Drummers), but there are differences that make LZ less "metal" than BS.

Page played most riffs as a single note part doubling what the bass did an octave higher, while Tony Iommi played power chords most of time. Power chords sound much heavier and are the foundation of metal.

The riffs LZ plays are more blues based than BS. BS's riffs sound more "evil" because of Iommi's use of minor /diminished scales.

Iommi also had a much more distored guitar tone than Page. After the first LZ album Page gets cleaner and cleaner while Iommi gets more and more metal.

A huge difference is in the production. While LZ was mostly huge drums and bass with trebly guitar riding on top, BS is monster guitars augmented by bass and drums.

While LZ may have laid the groundwork for metal, BS is the first metal band.