Regarding post-docs and their utility in matching

In a dilemma regarding this, do post docs in subspecialties of IM help increase chances of matching at good IM programs? The opinions are mixed on this online, with some saying they don't while some say they do. The most common argument I have heard against them is that a subspecialty research position is in a completely different department than IM so it wouldn't matter much. I would love to hear some personal experiences or thoughts regarding this and whether doing a post doc would be worthwhile.