I don't think they are the same. A plant that is suitable for xeriscaping is, one that is adapted to living in a dry environment. They grow well in xeric conditions, increasing in size, blooming and reproducing. The most obvious would be cactus. But a drought tolerant is, as the name implies "tolerant" of a drought.
A drought is an extended period of below normal rainfall. So a drought tolerant plant is use to a "normal" level rainfall for it's native area, but it can tolerate less for an extended period. Drought tolerant plants may take a little longer to show signs of stress , but they will suffer and eventually die, if not returned to a more "normal" level of irrigation.
