First off, I assume you mean MacBook Pro, not "PowerBook pro".
Might as well use the HDMI connection since all you need is the cable on this computer. That's what I would do.
If you want to use the Thunderbolt port (which includes all the DisplayPort connections), you will need an adapter. Your old computer vintage will determine if the adapter is useable on your new computer. The Thunderbolt port will accept a mini-DisplayPort plug.
Using HDMI by default from a MacBook Pro to external monitor actually displays the wrong color profile (In short your MacBook Pro thinks that the monitor is a TV)... It can be fixed and over written to look great though and just using an HDMI cable is smaller and more streamlined than a thunderboldt (or mini display port) to VGA or DVI adaptor. HDMI and DVI are always better quality than VGA.
For anyone else who's out there searching google looking for answers thank Mathew Inkson and his write up: http://www.ireckon.net/2013/03/force-rgb-mode-in-mac-os-x-to-fix-the-picture-qua lity-of-an-external-monitor
Thanks for your response. I have had three monitors connected (HDMI) to my late 2013 MacBook Pro running Mavericks 10.9.1 The first was an older Samsung (PA2370) that worked fine, great picture. I then ordered a Dell U2413 that gave me a horrible picture. It showed many of the symptoms described in the above discusion by Mathew Inkson. I called Dell and after 2 hours of talking with tech's who seemed to know less than i did, I was finally told that Model U 2413 was not compatable with my Mac. I retured that monitor and began a new search for a new monitor that was good for photography editing and that was compatable with Mac. I ordered a new Asus PA249Q and it seems to be working well with my MacBook pro HDMI connection.
So now I am confused? Am I not getting the correct color space to run my monitor even though it looks as good or better than my previous Samsung. Shoud I apply the fix from the above article or has this problem been fixed in 10.9.1. If I apply the fix and it doesn't work or makes my monitor look worse, can i go back to original setting.
I want to be sure I am getting the full power of my new monitor.