I don't think that there's a lock made by man that can withstand power tools for any significant length of time. But, the more cutting that's involved, the longer it's going to take, and from my research, those NY type Kryptonites that lock on both ends of the U may require two cuts to pry it apart far enough to pull the frame out. Also, all metals are not created equal. Some harder metals like in that U-lock are extremely time consuming to cut. At my work, I've used angle grinders and cut off wheels plenty of times and some steel are tough. Some are not.
And ofcourse, more locks the better. If you have a NY U-Lock as well as say a cable lock with it's own lock, that's going to require a few more seconds to defeat.
If you take power tools out of the equation, a heavy duty chain such as the NY series or Kryptolok Series 2 or 4 may work well against common U-Lock defeat methods using a car jack. Those chains are thick enough to easily withstand a small to medium bolt cutter and the locking shackle has quite a bit more bite than a typical U-lock.