I use an Edge 520 for cycling and a Vivoactive HR for everyday. I was surprised to learn that the Last Sport and Last Ride apps on the Vivoactive HR are not pulling data from Connect -- the Vivoactive HR considers only activities that are logged using the Vivoactive. Same with PRs: the PRs displayed by Vivoactive are PRs logged by the Vivoactive, not the user's real PRs tracked by Connect.
Support says this is FAD, but that seems surprising to me. Not sure the designers/Product Managers really considered the use cases with multiple devices? You would think that Connect would be the aggregation point, and the individual devices would compare device-level PRs and last activities to those logged on Connect, and replace device-level with Connect data if it is more accurate?