The ascent gained on my 705 is always about 10-11% less than what's calculated by Garmin Connect or Strava after I've uploaded the ride data. I have more confidence in the 705's altimeter based estimate since I've actually tested it versus USGS topo maps. I usually start and finish the ride at the same point so I also correct the ascent nos. based on the different altimeter readings before and after the ride.