maximus vi extreme - THE extreme overclockers motherboard to get if you will be watercooling or LN2 cooling. More features than any other z87 board on the market right now, packed with anything and everything you will ever need to take your performance to the next level. PCI-E on/off switch for quick switching from 4 to 3 to 2 to one way sli/crossfire. extreme digi+ engine III giving stable clean power to components on the board. vast array of ROG features such as rog connect, and the ROG overclock panel for quick voltage changes during benching.
maximus vi formula - The gamers motherboard, packed with lots of nice features, not quite as many as the extreme, basically everything considered "extreme" has been cut off, but asus continues to price it at extreme levels. *disclaimer* the next couple sentences are purely opinion based* - Cheapo plastic shroud put on top of the motherboard to make 12 year old fangirls squeel in glee, looks like a cheesy space bunker wall ripped out of the original Halo game. The included waterblock channel was made out of aluminum, and anodized, and asus swear up and down that it will not have any compatibility issues with copper waterblocks if you choose to water cool it, but tests have shown no matter how well it does, even the slightest scratch when installing a fitting into and boom, galvanic corrosion - ruined water blocks, fittings, motherboard heatsink, and possibly pumps due to clogging from debris. *end disclaimer* - still has nice overclocking features and gaming features for every day use, better than most motherboards out there atm, even if it is trying to get you focused on the plastic shroud and built in watercooling features.
maximus vi hero - The intro gamers/overclockers motherboard, everything you would want from a ROG motherboard, the looks, the features, the quality. While not as extreme as the extreme motherboard, this motherboard has virtually everything you would need for non super extreme LN2 overclocking. two way sli, three way crossfire compatible, extreme digi+ III engine for heavy overclocking just like the extreme motherboard. While not having as many features for heavy duty overclocking as the extreme board, it comes with everything you need if you are the average gamer/overclocker. On top of having the badass ROG look. And this board wont kill your wallet. I personally own one and have a 5ghz 4770k in it. Worth every penny.
All just my personal opinions really, hope any of it helps.
For you i would say go for the Extreme motherboard, very much worth its weight in gold. Probably avoid the formula board. Hero if you dont want super extreme overclocking for liquid nitrogen, but still want 2 way sli and the awesome looks of the maximus boards.