Mediavine names 8,643 sites in its seller file against SHE Media’s 1,599, and 49 publishers run both on the same pages. Reach is only half the question though — the authority spread below shows what kind of sites each one actually carries, which is what determines whether you would be accepted and what the inventory is worth.
Mediavine is the more selective of the two, with a median authority of 29 against 17. The overlap figure is the practical one for a publisher: 49 sites already treat these two as compatible rather than mutually exclusive.
On 7,044 more sites than SHE Media — the larger footprint of the two.
Median authority of 17 against 29 — more of its sites are still small, so a growing site clears its bar sooner.
They treat the two as compatible, not either/or. The “Also uses” column on either network page lists them.