First, a quick correction: 1500-1700 is not known as the "the long Middle Ages"; rather, "long Middle Ages" refers to the scheme that extend the medieval period into the 18th century (which would be considered "early modern" by standard historiography).

Some historians championed a lengthened medieval period as the medieval period was rehabilitated in historiography from the "Dark Ages" into something much more vibrant over the course of the twentieth century. Not surprising, early modernists (ahem) generally reject the idea that their period should be subsumed into the medieval period; while those championing an extended medieval period, like the late Jacques Le Goff of the Annales School, tended to study centuries within the traditional medieval periodization (~500-1500).

Why the distinction matters: long medievalists (a term I just made up, as far as I know) engaged, and really are still engaged, in a long-term struggle to overthrow misconceptions about the medieval period. Their efforts to extend the medieval period focused primarily on drawing out continuities between the medieval and early modern periods—like the centrality of religion to everyday life and a non-empirical worldview—instead of focusing on the differences. Previously, historians made the Renaissance, which roughly bookends the medieval period, a period of exceptional change in technology and thinking that made the medieval period look superstitious, backwards, and dirty. The reality is that the medieval period was less superstitious and dirty than many people believed, and the early modern period was less a magical transition or rediscovery of civilization than some thought.

While the rehabilitation of the Middle Ages is itself not controversial, the reperiodization of the "long Middle Ages" is definitely a controversial idea. Although historians will regularly disavow periodization as an arbitrary distraction, no one wants their pet subject to become someone else's field. As such, many early modernists make significant efforts to draw connections to modern institutions and ideas within their work. Julius Ruff's Violence in Early Modern Europe, 1400-1800 is a good example of this trend, as is Jacob Soll's The Information Master, which attempts to draw similarities between Louis XIV's minister Colbert's information-gathering techniques and modern information giants like Google. Early modernists will also often draw on ideas from Michel Foucault and Norbert Elias, with caveats, to illustrate the "modernizing" process as beginning much earlier than a "long middle ages" would suggest.

It really comes down to personal preference and the subject in question. There is no singular correct way of timetabling historical periods. The 16th to the early 18th century are often refered to as an extension of the Middle Ages because they still featured many aspects which are generally considered to be 'uniquely' medieval. History is mostly an evolution, not revolution. Hence why these transitions can be different depending on where you look.

I'm going to bed, but I might look tomorrow. Yet this is a very commonly talked about topic in accounts of general or global history. You could try looking for global history specificaly.