Dave
I always thought they were the same, just one output was MiB and the other MB…
There are a few different ways of measuring ram usage as well and what is included in the reading as really all the ram is used IIUC.
You may find that dumping the cached pages and such will “align” the readings.
Running
cat /proc/meminfo
should give you a list that you can filter through yourself. You might find that you can add and subtract those numbers to make up the output of the the other programs.
Computers are like air conditioners. They work fine until you start opening Windows. ~Author Unknown