Which of these computers would better serve my needs?

I am designing websites and will be using graphic software and want to be able to upgrade as needed. a href="http://www.shopping.hp.com/store/product/product_detail/AY604AA%2523ABA" rel="nofollow"http://www.shopping.hp.com/store/product…/a OR a href="http://www.dell.com/us/en/home/desktops/desktop-studio-xps-9000/pd.aspx?refid=desktop-studio-xps-9000&s=dhs&cs=19&~oid=us~en~29~performance-desktops-03~~" rel="nofollow"http://www.dell.com/us/en/home/desktops/…/a and what do you think of the company support of Dell and HP.