When you run 'startx' you are still logged in in tty1, so what you see is not bootmessages but messages from your X-session. This is not so good for security reasons. If someone is near your computer when you don't see it, they can press ctrl+c in tty1 and cancel your x-session, and still be logged in as you.
What you can do is either start X automatically when you login in tty1 (the other ttys won't be affected), by adding this to your ~/.bash_profile:
[[ $(fgconsole 2>/dev/null) == 1 ]] && exec startx -- vt1
That will start your X-session in tty1.
If you dont want to start X automatically you can create an alias for it. You can get some more ideas here