I would advise deciding what color interior you want and check out both materials in person in an X1 since you will be the person that lives with the choice. And if you are buying instead of leasing, go to a used car lot and see the looks of BMW leather in a couple of different cars after 6-7 years. In addition, you should think about why you want the X1 since it may help make this decision a bit easier. When I listed my reasons, a luxury looking interior was near the bottom of my list. In my next car, I wanted fun to drive/rwd, good safety, good residual value, > =32 mpg highway, easy to park, decent cargo space, low noise, high tech features all before a premium feeling/looking interior.
In entry level Mercedes and even BMW's , I think the leatherette is nice enough that you really don't need leather. Leather does look a little more premium over the first couple of years of ownership at least but I like the fact that leatherette is very easy to clean and doesn't appear to be affected by the sun.
If Coral Red leather was an option without ordering the sports line, I may have been tempted to buy the premium package and get that color since it does appear to be a fun color.
The general consensus is the black leatherette does a better job looking like leather then the beige leatherette. But the beige leatherette/leather gives more tones to the interior and brightens it up.
The way I figure it is if I regret not getting some of the options I bypassed, I will sell the car in 4-5 years instead of perhaps 6-7 years. The money I save can go to the new car.