Unless you have a good reason to use SWT, you should stick with Swing.  
SWT is non-standard, and it makes deployment much more difficult.  There
can be good reasons to use it, but presumption points the other way.

I have been using Swing for a few years but have been considering
switching to SWT because of Look & Feel issues.  However, IMHO Java 5 does
a pretty good job of looking native, compared to previous attempts by Sun
to get a Swing app to look native.  

Primarily I use Linux and a number of the Gnome themes render well under
Java 5.  It is not perfect and a little on the slow side compared to the
standard Swing metal theme, but it works well enough for me to stop
considering using SWT/JFace.

I believe there are GUI builders for both Swing and SWT available on the
Eclipse website, but I haven't tried them.

Regards,

Paul.