I ordered a Griffin Survivor and had it waiting before the 4S showed up.
My mom had an Otterbox Defender (I think) sitting around that she wasn't using so that went on my wife's 4S until she finds something she likes better.
I am very happy with the Survivor.
Both have a hard shell on the inside and a soft exterior. The Otterbox exterior is too soft though, it's tacky. Attracts hair and feels sticky.
The (charging) port cover on the Otterbox is flimsy and doesn't pop back into place easily.
All of the covers on the Survivor stay put and go back in nicely.
The Otterbox leaves the rear camera perpetually exposed, but the case around the camera on the Survivor does reflect the flash when used in low lighting. If I REALLY need to use the flash for some pics I take the camera out of the case, but it hasn't happened since my testing phase.
I bought the Survivor before I had the phone because I KNEW I needed a tough case. My last phone was beat up horribly. I drop them all the time. Shortly after getting the phone I ended up dropping the phone 4 feet into dirt at a Corn-maze repeatedly. Dusted it off and went back to whatever I was doing.
Cases like these add bulk, but if you tend to drop your phone, have kids or pets etc they are a good investment. Your decision ultimately should come down to aesthetics and feel, as there are multiple products with adequate protection. Find one you like.
I have a penchant for hot pink, and found the Survivor in HP with the redesigned notch for holding the camera cover out of the way. Score.