PubGalaxy names 2,610 sites in its seller file against Playwire’s 1,039, and 39 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.
Playwire is the more selective of the two, with a median authority of 32 against 18. The overlap figure is the practical one for a publisher: 39 sites already treat these two as compatible rather than mutually exclusive.
On 1,571 more sites than Playwire — the larger footprint of the two.
Median authority of 18 against 32 — 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.