My experience with Alta Vista was that sometimes it seemed to go "off-track", answering, not my question, but a similar question. When I tried to refine my query, it still seemed stuck on what it thought I asked before, not what I was asking.
I later found out that they used "Bayesian Logic", where the answers to the previous questions guided the answer to the new question. No wonder I had this problem!
When Google came along, of course I went with them, and still do. They are still the #1 Search Engine, although some of their other services, like Google Maps, have become untrustworthy.