the first one was published in 1992 (1994 revised),while the second was 2004.
the first one focused on the usage of similiar words,and each word was introduced by a concise definition and a sentence,while sentences were not given to each words in the latter.however ,the latter contained not only the syn,but also the antoyms,as well as the related words.
from my point of view,they were different.you'd better go to a bookshop to choose the one you really need.it seems to me i like both them.