I think it makes sense to track things, that may change statistics. Sometimes you try to find many large caches. If one of your founds suddenly gets converted into a PETling and becomes a micro, this is frustrating - especially if you do not know what it was, that changed your statistics.
So the size, placement date, cache title and maybe even attributes are things that make sense for me to track. Also, it happens that a multi or myst turns into a tradi, so the cache type also makes sense to be tracked.
Once everything is tracked, it would be great to have a filter where you can find caches among your founds, that had changes.