That obviously depends on what you'd be using the points/miles for. DL points are good for Sky Team rewards. 50k is half of a business class US-Europe redemption. And, using Sky Team partners as opposed to DL, you'll not find much trouble booking that business class travel at that low level. Although, you may have trouble getting to your international point of departure using the Sky Miles unless a Sky Team partner can cover that too (for example, Alaska).