PingStack offers Free Trial, but Uptime Robot does not.
PingStack is designed for Medium Business and Small Business.
Uptime Robot is designed for Large Enterprises, Medium Business and Small Business.
Pricing for PingStack Starts at $9/Month whereas for Uptime Robot Starts at $4.50/Month when Billed Yearly.
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 Uptime Robot includes Uptime, StatusCake, CHEQ.ONLINE, DevMonitor.io, UpTime.onl, SiteUptime, Monitor Buddy, SolarWinds Pingdom, pingnow.io and PingPing.