Install Redis RDB Tools from here:
Take a snapshot of each redis db
$ redis-cli save
Copy the snapshots to somewhere else
$ cp ~/dump.rdb ./dump-a.rdb
Use rdb tools to dump each db, stripping out bracketed positions, and sorting
$ rdb --command diff ./dump-a.rdb | sed s/\\[.*\\]// | sort > ./sorted-a.out
Diff the two files
$ diff ./sorted-a.out ./sorted-b.out
Phew!