AFTERPAD

I have owned and or extensively used the Moga Rebel, the Mad Catz Ctrl i, the Steel Series Nimbus, and the Horipad Ultimate.  Contrary to Kevin's review on the site, I have to respectfully disagree with him and say the Horipad Ultimate is by FAR the best Mfi controller out there.  So much so that I now use it for all my OpenEmu gaming on my mac (instead of my beloved DualShock 4) and am trying to set it up in windows as well. 

As primarily a retro gamer, I've found the dpad is the most important part of the experience for me and the Horipad comes through in spades.  Yes, the triggers are floaty but I've found them to be totally usable, and the primary L and R buttons are absolutely perfect.  But the build quality is as high as any controller I've used and the "feel" of the buttons and d-pas blows all the others out of the water. 

The Nimbus is a close second, but I found the dpad to be inferior because of its odd size and shape.  Also, there is plastic "ridge" of some kind immediately below the dpad and buttons on the controller that I found dug into my thumbs and made the unit very uncomfortable to game with.  Of course YMMV, but as both are available in the Apple store you can try before you buy.

As for the other controllers, forget they exist.  The Ctrl-i would be totally fine if it didn't have a  dpad that is quite literally unusable. 

And one additional advantage of the Horipad is that you can easily mod it to have an iPhone "grip" of sorts. Because it is flat above the menu button, you can stick a small iPhone dashboard mount on there.  I use one by Scosche.  By cutting the top and bottom of the sticky part of the mount, It's small enough to fit on the unit with minimal overhang and still be able to see the paring lights.  Also, the automotive-grade adhesive they use (no idea what that means but they say it on the box) is strong enough that with 2 months of daily use and travel in my bag, it still holds my 6 plus securely. 

TL:DR: the Horipad ultimate is the best mfi controller and can be modified to have an iPhone grip.