Strava just uses positioning data from your phone - so it is no more or less accurate than that. You can increase frequency of GPS updates, which considerably improves pace data. This is a phone config change, nothing to do with Strava.
My beef with strava is the altitude data. They won't pay for this, so they crowdsource it from devices using Strava, and record in intervals greater than 10m. That's a pretty coarse measurement.
For me, it offers, for free, a way of recording and comparing runs. I don't use it for anything else.