Bottom line: I'm using a Ballistic SG MAXX with an Invisible Shield screen protector.
Since I got my iPhone 5c, it's been inside an Otterbox Defender case. I didn't even have a chance to handle it at the store. This is much the same situation I had with my iPhone 4s, until such time as I needed to wash the case.
The big difference between the two Otterbox Defender cases was the fit. Where the iPhone 4s case was sloppy, the 5c case was taut, and vice versa. There was one huge problem: the fit of the screen protector. It didn't fit against the surface of the display, so that there were two presses--one press against the screen protector and another as the screen protector contacted the display. It made for poor touch screen performance because you wouldn't actually end up pressing precisely where you intended.
There seem to be hundreds of reviews on Amazon.com about the screen protector, and I was told by the salesperson at the Sprint store that three of his customers simply cut away the screen protector. However, on a US$49.99 product that should have been designed correctly, I wasn't about to damage it intentionally. There is something about being first to market with your product, but if being first brings you hate mail because of an incorrect design, why not wait?
So, I bought a Ballstic SG MAXX (apparently renamed to Tough Jacket Maxx) for my iPhone 5c. Apparently, the Hard Core case is not available for this device. Amidst the Christmas buying and shipping season, I waited a few days for this case to arrive from the Miami, Florida area, normally an 24 hour drive for me.
It arrived in a fairly big box with only the case in a Ziploc-type bag with the paperwork inside it. There was no packing. There were no instructions but there was a "Ballistic" sticker that I could use along with my Apple stickers.
Getting the phone out of the Defender case was the big deal. I suspect no one at Otterbox considered that one would remove it, ever. Taking away the rubbery silicone layer isn't difficult. Being careful avoids damage, of course. Removing the hard shell is the painful part. As with the 4s case, looking from the back, you release the clips on the left and right sides. Replacing the 4s case clip on top is a !@#$ tiny piece of plastic which acts as a retainer on the 5c case. It's impossible to grasp, and I couldn't seem to make it collapse by pressing on it. Somehow, with a little force, I managed to release it. At that point, you tilt the back and remove it (as with the 4s case), and remove the phone from the front piece.
The SG MAXX case was quite different. The rubbery silicone fits on the phone first, along with the somewhat rigid screen protector, which is a separate, loose piece. You then add the hard shell, and work with the silicone piece to make sure everything is covered properly. It can be placed in the holster at this point. There was an included graphic on the interior of the holster depicting another product, but reminding you to face the display inward to avoid damage.
It works quite well, although the screen protector gives a sparkly, matte look to the display. However, as a thin sheet, it can be removed easily and something else, such as Invisible Shield can be put in place instead. Having been out into the world to use the phone and case, I've noticed something odd. It doesn't want to stay in the holster all that securely. Maybe, it's something I've done and it's wider than it should be. I'll keep working on it. Update 2013.12.29: That didn't take long to annoy. The fit of the screen protector is not quite right, and changes the more you mess with the case. I finally removed it and bought an Invisible Shield protector for another US$14.95, which means that I've spent over US$100 on two cases and one screen protector. Grrrrr.
For those trying to impress people with your Apple-ness, the logo on the back is not visible with the Ballistic SG MAXX case. With the Defender case, it wasn't centered properly, but it was visible. My take is that it's better not to show it. If people think that they can steal something to sell it later, they will try. Besides, it's just a phone, and it's not worth your life.
I'm not quite sure whether I'm going to try to return the Otterbox Defender to the point of sale or request an RMA to send it to them for a warranty exchange. They really need to know what's wrong with it, although I suspect that they know quite well, and have re-designed the case after getting an iPhone 5c.
Update 2014.06.12: This morning, the little flap over the Lightning connecter port broke. I guess it shouldn't be totally unexpected. I have to move it out of the way frequently, and the phone goes into the holster and that goes into the pocket a lot. Will I notice a difference in protection? Probably, I won't. The rest of the case, both hard and soft parts seem to be okay.
Update 2014.08.24: A month or so ago, I was in a mall and someone selling cases was pushy and told me that Otterbox had glass as their latest screen protector. Recently, Invisible Shield also has a glass version. Certainly, it would be helpful for maximum display clarity. My Ballistic SG MAXX case continues to be fine, even after dropping it a few more times.
Update 2014.12.13: I've switched to the iPhone 6, and I refused to buy another Otterbox Defender, since it was so difficult to remove. All the Sprint kiosk had otherwise, was a Griffin case that said it had been tested to 3 feet. About a week later, I found some Best Buy-only Ballistic brand cases at, you guessed it, Best Buy. I bought the Tungsten Tough for $39.99. It mostly seems like the SG MAXX/Tough Jacket Maxx without the holster clip, but it has an aluminum plate on the back, as though it is hiding that it is a Ballistic product.
Update 2016.11.16: I've got an iPhone 7 and a pair of Ballistic cases of it. Read more here.