If you have a Garmin, you actually have a lot of the features Strava offers through Garmin's free service. I don't think you even need a Garmin device to use it if you upload your data manually.
Maybe serious athletes and socialites rely on some specific Strava only functionality, but I find the Garmin service has pretty much completely replaced Strava in my own usage.
This is how I record all of my activities to Strava. There's no need for an external sync service.