Your questions is pretty close to garbage. There are times when DB2 makes sense, just as there are times when VSAM makes sense. And there are times when using SORT makes sense. When a situation mandates DB2, asking whether it is "<more> efficient and faster" is like asking "How high is up?" The answer won't really matter since the software is required.
VSAM is a way to access data in a file. DB2 is a data base management system. Comparing the two is like comparing Windows Media Player to a Macintosh. Yes, you can do the comparison, but under almost all circumstances the results of the comparison mean nothing.