CompareADAM is a tool for pairwise comparison of ADAM files (or merged sets of ADAM files, see the note on the -recurse{1,2} optional parameters, below).
FindReads is an auxiliary command to CompareADAM -- whereas CompareADAM takes two ADAM files (which presumably contain the same reads, processed differently), joins them based on read-name, and computes aggregates of one or more metrics (BucketComparisons) across those joined reads -- FindReads performs the same join-and-metric-computation, but takes a second argument as well: a boolean condition on the value(s) of the metric(s) computed.