You can totally make Pot Roast in a crock pot, however, I have found that the meat ends up being a bit too dry and the dish overall lacks flavor.  Dutch Ovens tend to distribute and retain heat better than a Crockpot, which leads to more flavorful and tender meat. Another perk is you can sear your meat in the Dutch oven, then move it straight to the oven, making it a one-pot meal.