If you've got an external monitor I wouldn't recommend anything. YOU need to base your decision on budget and space considerations. Personally I have two Samsung 172x LCDs, not that cheap though but the bezels are pretty narrow so I can stack two side by side and have the TL stretch accross them.
I just got a Samsung 910t 19" flat panel, to replace my 19" space hogging CRT.
I love the fact that I can rotate the panel 90 deg. and put projects with many tracks on it. My other is a 17" widescreen.
here's a PIC
excuse the mess