He's comparing it to building emacs from source. He's quite obviously trolling: Emacs has 15MB of C source and header files already.
On my machine (2010 15" MBP) a configure alone takes 20s, which is about 3 times the loading time of an empty IntelliJ (no project), and about twice if loading a preexisting (cached) project. A `make` of 23.2 takes nearly 3 minutes. Unless he's trying to launch an IDE with no free RAM or building an already-built soft (or a networked build), his declarations hardly make sense.
I remember when people joked that Emacs was a memory hog "eight megs and constantly swapping".
Eventually Mallocs All Computer Storage.
Emacs Makes A Computer Slow.
About the only one that's still true now is this:
Escape Meta Alt Control Shift.
A once-in-a-lifetime experience though, I start the emacs server on boot so I can start clients much faster, which means it's always running as long as my computer is on, and it's never had any issues other than that one time.
Why? You start it once, the first time you want to start developing. And you never close it until you reboot the machine.
Same as with Emacs, start it, have it enable server-mode automatically, and until you reboot you go through emacsclient.