I am using Runtastic, MapMyRide and Strava on my two phones and I run two app at the same time just for fun. Runtastic wins as it has heart heart info for free and it also audio announce heart rate zone change. It has auto pause. They are all pretty close in the stats, except for calories burned. It varied widely!

I use to have a phone (Note 4) where I would loose the GPS signal under trees.

I now have the Note 5 and S7 and they both have great GPS signal. No endorsement on Samsung. LOL. Thats one of the reason why those phones have glass back (GPS?) and 4 wireless charging.

One way to test is get an app "GPS Test" and I get 3D lock signal inside building. That means you have great GPS sensitivity. Did you do this test?