I need an opinion for a phone system.?

I found the Avaya Partner 18D ( http://www.etelephonesystems.com/images/vcat/111452569400002.jpg ) and the Avaya Partner 34D ( http://www.teldatawest.com/images/partner%2034d%20euro%20series%202.jpg ) For about the same price. I need 4 phones. I like the 18d look better but I want a second opinion. I could use the 34D as a master phone on the system. So... My question is should I purchase ONE 34D and THREE 18Ds or FOUR 18Ds?