If you really only keep your run on a route that you have measured the distance of and know well, then GPS would be an option that you may not need.GPS option is perfect for runners who love to discover different tracks, roads and etc. There are many adventurous runners who run in new places every day.
GPS option is good when you run in unknown areas and you’re afraid of getting lost. If you really want to run on the same track every day, GPS is unnecessary. What’s more, watches without GPS tend to be much cheaper.
Instead of GPS function, you should look for features more connected with creating a running plan and all basic metrics to show you your results even on this one track you use.