Depends on what you want to do with it. PVR? Streaming? Games? Skype?

Are you planning on running Windows MCE? Plex? XBMC?

The new NUCs are slightly larger (and uglier IMHO), but can use a standard 2.5" drive and use the newer, more energy efficient Haswell processors.

The previous generation require a mSATA drive, which can get pricey in a hurry. Here's a great price on a previous gen Core i3 NUC