I haven't used the Sportdog unit but I have several years of hard field use on a Garmin Astro unit and I'm very pleased. I've used it on four different dogs in all kinds of conditions and it works fine. If you watch for Cabela's sales, they'll probably have the Garmin Astro on sale again for $499 with free shipping - it's been at that price about 3-4 times since Xmas. Based on what I see for prices at Cabela's with the Sportdog 1.0 and Garmin Astro units currently priced within $40 ($559 vs $599, respectively), and with my field experience with the Garmin, I would recommend the Astro unit. Another big plus IMO for the Garmin units is their ability to accept the property ownership chips from Onxmaps (
https://www.huntinggpsmaps.com/). I've used their chips for MT and AZ/NM/UT/CO, and found them to be invaluable in determining property boundaries.