The advantages of the wheeled Stryker over tracked vehicles are less maintenance, higher mpg, quieter, faster on roads, less wear & tear on the highways & byways than tracks, and it carries a crew plus a full infantry squad & all their gear--something a Bradley cannot do.
That all translates to less cost, a smaller logistic tail, less vehicle "down-time", less annoyance to the locals as you aren't shaking them out of bed as you go by or grinding up their roads & curbs, and better ability to escort convoys & then chase down the bad guys either mounted or on foot. A pretty good fit for the situation in Iraq right now.