All good recommendations.
@Bigpoppapump Glad you got to ride Erwin, as it really has everything you'd want in a trail ride, and a beautiful property. We're doing a MTB campout there with our scout troop soon since it has good campsites, too.
I love Horseshoe - probably my favorite more compact trail in the area, with a little something for everyone. Northshore gets all the attention, but I find it frustrating, partly because I struggle with it (and also because it's usually fairly crowded and has its share of Stravaholes flying through on the regular). I rode Knob Hills once and was really disappointed given the hype.
Big Cedar is my favorite larger trail complex, with everything from green trails to super-difficult blacks and a jump line, and it benefits from Escarpment terrain so it feels more like the Hill Country (more elevation, rocky, lots of cedar/juniper). The knock on Big Cedar is that it has 20+ miles of trails and they're not always well-marked. It took me a half-dozen visits before I started to feel like I really knew my way around, and even still there are 3-4 trails I haven't been on yet. Also, it's closed on Sundays until 1pm and all day Monday, since it's private property. Boulder Park is great, too, with somewhat similar terrain - just more compact.
If you're in North Dallas/Plano area, Katie Jackson is a fun little neighborhood trail. It has a couple flat and flowy loops, and then a more difficult loop (yellow) with some nice but manageable drops.