Terminal 2 has the longest lines at the security check.

At the time you are talking about, it's hart to say which will be longer as it is kind of in between. But both security lines are almost never long at the same time.

I would probably arrive around 6:30 or so, and would try the Terminal 2 line first. If it is really long, then I would go back to Terminal 1 (which would almost for sure be shorter).