With both emacs and vim you can certainly edit 500MB file. I concatenated all sources of recent Linux kernel 4.6.3 once. From what I remember it was all .c, .h and .S files. Resulting file has 542MB and 19'726'498 lines. I did it to test the text editor I am working on.

Some stats:

  $ time vim -c 'edit kernel-total' -c q
  real	0m8.162s
  user	0m7.687s
  sys	0m0.398s
  $ vim kernel-total ^Z
  $ ps aux | awk "/kernel-total$/ || NR == 1"
  USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
  hawski   10467  2.7 17.1 805120 670988 pts/2   T    17:41   0:07 vim kernel-total
  $ time emacs kernel-total -f kill-emacs
  real	0m7.155s
  user	0m6.869s
  sys	0m0.237s
  $ emacs kernel-total ^Z
  $ ps aux | awk "/kernel-total$/ || NR == 1"
  USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
  hawski   10825 43.8 14.8 857484 581152 pts/2   T    17:47   0:07 emacs kernel-total

With vim editing is quite smooth and with emacs it feels laggy. I only edited a bit, like entering a new line here and there, moving few pages down, going to the end of the file and to the top again. Saving is sluggish.