Went to all three outlet malls in the last month so I could stop guessing which one is actually worth driving to.
Allen Premium Outlets is the biggest and has the best store selection. Nike Factory there is legit. Downside: the parking lot on weekends is a warzone and it's outdoor so summer shopping is miserable.
Grand Prairie Premium Outlets is smaller but less crowded and closer if you're coming from Fort Worth. The Coach outlet there had better deals than Allen when I went.
Tanger in Fort Worth is the weakest honestly. Fewer stores, older layout, nothing you can't find at the other two.
My verdict: Allen for selection, Grand Prairie for convenience, Tanger only if you're already in west Fort Worth and don't want to drive.
Allen Premium Outlets on a Wednesday morning is the move. No crowds, fresh restocks, and you can hit every store in 2 hours.