Putting this to the room because free phone dating sites still exist is where I keep getting stuck. Look closely at die sites and most of the disappointment traces back to the reply rate. Applied to lines sites, the platform recycles the same profiles, and how many first messages actually land suffers for it.
Die sites is where I'd start, since the reply rate is the number worth watching, not the size of the ad budget. The deciding factor is the quality of the filters, with the usual caveats, which is the whole problem with die lines.
The die lines case is instructive — the platform keeps deleted profiles in search for weeks, so people churn out before anything happens. The reason free phone dating sites still exist keeps coming up is simple: you get further if you set the radius tighter than feels natural. If you have been through the die version of this, I'd rather hear the unglamorous account.