It is hard to say whether there is a big difference in thefts between the Kryptonite NY and cheaper U-Locks.
I have had a cable cut
Anyway, I do like the Kryptonite NY, although it is HEAVY. The cable might not be bad to augment the security for the front wheel.
Of course, also pay attention to HOW TO LOCK A BIKE.
I usually like to snag Frame + one wheel (usually rear, but sometimes front) + bike rack (or in some cases good post).