PaintShop Pro 5.0 vs. Photoshop?

I'm a graphics newbie.  I downloaded a copy of PaintShop Pro 5.0 and found
it easy to learn.  I also read,
in David Siegel's Killer Web Site book, that Adobe Photoshop is what all
the professional Web designers
use.

My question...what does Adobe Photoshop have that PaintShop Pro 5.0 doesn't
have?  Is it worthwhile for a
novice like me to spring for the money for Photoshop, or can I do
everything I need in PSP?

PS.  I also found some great PaintShop Pro tutorials at:

http://www.sumrallworks.com/freebies/buttonhole/psp/tutorials/tutorlisting.htm
http://members.tripod.com/mirar/tutorial.htm
and
http://www.pspro.ml.org/text/

Ira

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