Overclockers favor the Extreme3 Gen3, but I prefer ASUS boards, although the LX is lower grade than the P8Z68-V/Gen3 I usually recommend for Z68 (I use the Pro version) with PCI-e3.0 support, and better Intel LAN chipset. Also, over the LX the LE has onboard USB3.0 header for front panel support.
Yes, listen to Neon, look at his signature, he's almost 1.5GHz over stock speed!!
The Extreme4 and Extreme3 are very similar and popular for overclocking.
Gen3 means Ivy Bridge, so it has PCIe 3.0 support if you have an Ivy Bridge CPU, and good overclocking capabilities. I just prefer ASUS boards as they've never let me down but that doesn't mean the Extreme3 isn't a good board. Look at the reviews and do a search within them for whatever CPU you plan to use and you'll see a large number of totally pleased OC'ers.