How much time do you have on your hands? (Or want on your wrist?)
The short answer from my perspective is, get a Garmin Forerunner that matches your budget. They’ll all have more features than you need, but what’s important is a good GPS system that picks up satellite well in forested areas, and my experience is that Garmin does pretty well there. I have an old Garmin Forerunner 620, which is a fairly high-end model, and my experience is that it acquires satellite faster than the newer (but cheaper) 235s that some other High Nooners have.
The long answer, if you’re really, really bored, is to go to the DC Rainmaker Web site and read his reviews. This guy is insanely detailed, and as a real triathlete and serious geek, he really tests the heck out of every device on the market. And there are a LOT of them. Most will work fine for what you want.
If you were interested in more of a smartwatch, an Apple Watch will do a pretty good job at just marking your trail; it’s not nearly as good as the Garmins for on-wrist usability while running, but it’s a much more capable device otherwise.
In the interests of supporting local businesses, perhaps @Ian can say what he recommends and sells in the store. Last I looked, his prices were pretty much the same as online retail prices.
One final note. Only very occasionally have I had to rely on my GPS watch’s map to find my way back to a road or trail. That can be difficult (or impossible on some models) to do, so if that’s useful, make sure a visible map feature is an option, and try it before relying on it.