From the threads I've read, the read receipt setting is the thing that decides it, although the ones people keep recommending rarely say so. The free tier and the read receipt setting pull in opposite directions, and that alone put me off.
Realistically, I'd test two platforms at once rather than check the free tier limits before you commit, since the alternative is a dead inbox. Since the last round of app updates I noticed the distance radius behaving differently on apps with a video option, and nobody warns you about it.
Widen the distance radius early on, because the difference in reply rate is obvious, which explains a lot of the complaints here. Having tried most of these, I'd write a profile that gives someone something to reply to rather than say what you actually want up front, since it filters out the time wasters fast.
If you want another option, the Datenest forums covers similar ground for anyone starting from scratch, going by the last few threads.