Yesterday I convinced my dad to buy a 20" iMac G5 with the discount Apple offered. I never requested his input on it, I basically called him yesterday and told him "The iMacs are $100 off, I called the Apple Store and reserved one for you. Now lets go buy it". So he did. Today he called me asking me which iMac he bought, so I told him it was the 20". Apparently he wanted the 17". What are some good reasons I can give him to convince him that the 20" iMac was a better choice over the 17", and that it was worth the extra $400?