And it depends on what you mean by "better." I assume you mean "cheaper."
To oversimplify: Who's going to sell it cheaper: The bank or the bank? Yup, that's right. In both cases, the bank determines the price. In the case of a foreclosure, the bank actually owns the property. In the case of a short sale, the owner is the purchaser from a few years ago. However, the sale is contingent upon the bank's approval of the price.
And in both cases, the bank largely uses its determination of the value of the property. That determination comes from what's called a "BPO" or broker's price opinion. It's like a quickie appraisal, but generally a lot less accurate. The one major difference is that foreclosures and short sales are handled by two different departments within the bank. So you'll frequently see a variation in how the actual transaction is handled. And generally--though not always--foreclosures are comparatively easier than short sales.
But if you mean: What's the better value? There's no "a foreclosure is better than a short sale" rule of thumb, or visa versa.
And to complicate things further, sometimes a conventional sale is best. It certainly will take less time than a short sale, and often less time than a foreclosure. The home might be in better condition--people who lose their homes via foreclosure, especially, are tempted to trash the home. And if it's in an area with some foreclosures or short sales, the owner knows that, to compete against foreclosures and short sales, he/she will have to be price-competitive with them.
Hope that helps.