A full time Manometer is a good idea, you will learn a lot about your chimney, the MPD and the effects of the adjustments with a barometric damper.
A manual pipe damper will slow down the rate of flow up the chimney, if you have a strong draft, and have the air inlet vent in the stove mostly closed because of a strong draft, closing a MPD will do very little to reduce the draft. A barometric damper will reduce the actual draft, but not reduce the airflow through the pipe and chimney. Some chimney and stove combinations will benefit from a MPD, but I recommend a barometric damper first, with a Manometer hooked up, then if there still is way too much airflow through the stove, a MPD can be the answer, but only with careful use of a Manometer and CO detectors...
Basicly, a barometric damper is for any chimney, a MPD can be a help with an extreem draft and airflow problem. This is my take on the use of the two types of dampers..