If your only concern is watching movies, then either one will do. AMD CPUs are generally cheaper, while Intel CPUs offers better performance, but you don't need much performance for video playback.
For just a simple multimedia PC a cheap AMD Athlon is all you need. If your main concern is having a good functioning multimedia box and don't want to spend much go AMD. Although the price difference between AMD and Intel is not much of a difference, and Intel CPU's almost always outperform AMD. But for a simple movie box you will not be able to tell the difference between the two.