PingStack offers Free Trial, but pingnow.io does not.
PingStack is designed for Medium Business and Small Business.
pingnow.io is designed for Large Enterprises, Medium Business and Small Business.
Pricing for PingStack Starts at $9/Month whereas for pingnow.io Starts at $5/Month.
Some top alternatives to PingStack includes Uptime, Uptime Robot, Hyperping, DevMonitor.io, UpTime.onl, CallView 360, SiteUptime, pingnow.io, WatchSumo and Loadping.
Some top alternatives to pingnow.io includes Uptime, Uptime Robot, Easyping, Better Uptime, Hyperping, UpTime.onl, SiteUptime, Uptrends and Pingt.io.