The Maximus VI Extreme (12.0" x 9.6") is targeted at the serious no expense be spared, competitive overclocker / gamer.
The Maximus VI Formula (12.0" x 9.6") is targeted at the person with less time for tinkering who gives up some overclocking flexibility for the additional features .....maybe providing a workable work box with SLI capability so can have some fun with it to.
The Maximus VI Gene (9.6" x 9.6") is targeted at the college student, LAN party guy / gal or anyone who wants a smaller form factor and therefore chooses a micro ATX board but still wants to be competitive with SLI capability and all the other gaming, sound and OC goodies.
The Maximus VI Impact (6.7" x 6.7") is targeted at a user who wants an even smaller form factor and is willing to give up SLI capability to get it
The Maximus VI Hero (12.0" x 9.6") is the new boy on the block and was created to try and pull in those who were a bit shy of the cost of ROG boards and introduce them to many of the RoG features a lower cost of entry. On one hand it's been very successful in that a lot of people who always wanted to jump into RoG can now do so. OTOH, it's cost is creeping right up on the Gene at just $10 separation.
So now we get down to it.....what to get ? They are all RoG and all have great componentry (Black Wing Chikes, 10k caps, etc).... the feature set goes up as the price goes up. I see no reason to expect any longer life out of any one of them.
The main difference between the two is the mPCIe Combo II which Asus describes as providing mini PCI Express 2.0 (mini SSD connectivity) plus USB 2.0 plus Bluetooth and WiFi connectivity without having to give up a PCIE slot to get it which is huge and which most would consider well worth the $10. A Wifi card would cost ya $30 so if that's on ya list it's a no brainer. The smaller form factor gives ta more room inside the case if that's an issue.
http://www.asus.com/Motherboards/MAXIMUS_VI_GENE
mPCIe Combo II
The next evolution of the mPCIe Combo card gives you even better expandability with the latest standards in connectivity. It’s easy to install, and adds mini PCI Express 2.0 plus USB 2.0, which is perfect for connecting Wi-Fi and Bluetooth modules to give your desktop instant wireless. It also keeps a precious PCI Express slot free.
The compact but versatile card further future-proofs your build with M.2 (NGFF, Next Generation Form Factor) connectivity for SSDs. M.2 is a fast and power-efficient standard that aims to replace mPCIe and mSATA, designed to optimize SSD performance. mPCIe Combo II works with your high speed M.2 SSDs and makes the most of their potential, helping you reduce load times to make your OS and games even faster.
Is it worth it ? You tell me
.... again that answer will depend on what your needs are. I have no need for WiFi but for $10, it's a nice insurance policy in case ya find yaself working from temporary apace w/o a LAN connection. The SSD connectivity is interesting though I have never considered why Id want to use a mini SD instead of a full size one in a desktop....many mSATA are only SATA II but SATA III alsi around.
As to pricing, the Hero is already settling out in the market with price having dropped $20 in recent weeks to better compete with offerings from MSI and Gigabyte. I think we'll see another $10 or $20 drop before it settles out. Havent been following the Gene much.