I recently went into the store and saw both machines side by side. If you're one of those people debating over the 21.5 or the 27, definitely go with the 27. Not only are you getting a bigger screen size but also a better graphics chip and better processor. I experimented with the base 21.5" and I thought it looked outdated just from looking at the front. It just feels like one of those outdated computers that will become slow and useless. Also the upside with the 27" is that you can change your ram, which is a huge plus! So if you're deciding which one and money isn't a problem, go with the 27" this post is for people who haven't seen the iMacs in person and want an idea of what they are. I've been a apple fan for years, I also have 2 iMacs, a 21.5" and a 27".