[KronisLV]

This would matter if one of them had the limit that's much smaller than the others, which would lead to aggressive GC, which wasn't the case.

When working on the same project of a known size and using similar IDE functionality, different IDEs still had noticeably different performance characteristics (i implore you to try the same, especially with the same Xms and Xmx values set).

That simply leads me to believe that each IDE implements things differently, for example:

  - JetBrains have separate IDEs for separate languages (IntelliJ IDEA for Java, Rider for .NET, PhpStorm for PHP etc.)
  - NetBeans allows lazily loading support for different languages/frameworks/tools
  - Eclipse is generally viewed as a bunch of interconnected libraries/frameworks (JDT for Java, PDT for PHP etc.)

That's just one example of the architectural differences (which may impact which functionality is loaded when and how efficiently the memory is used), though it stands to reason that it's perfectly normal to observe them to act differently from one another, even in controlled circumstances, like the above.