Speck Candyshell Grip is my favorite case next to the Rock. It provides the most protection compared to all my cases. I liked it so much that I bought one for my wife (Black Note 4) and my daughter (Black 6). The Black and Grey version really goes well with the Space Grey on my 6 plus. It's the phone's black face and the dark grey surroundings/frame of the case that makes the combination really look good. But if I didn't have a SG iPhone, I wouldn't have purchased this case. Here is what I mean of the color combination on a black Note 4:
Best all around case for me that adds very good protection without adding much bulk and weight. Giving you more grip is just icing on the cake
I only have the Speck Candyshell Grip and love it. It add some bulk and weight, but much less than I expected. The case feels very sturdy to me. The main reason I love this case is the grip on this thing. And when the baby sees me using the phone and wants to play with it, I turn off the screen and let him hold it and even drop it with no fear of the phone breaking (but keeping an eye on him hoping he won't drop the phone screen first on a corner).
I don't have the Spigen you mentioned. But for comparison of another "tough case", I have a Ringke Max which is slimmer and lighter than the Candyshell Grip. Because of that...I'm not sure how well that one would protect against drops. The main reason I stopped using that one was the back is too slick and I feel like I'm going to drop the phone all the time.
I had both cases for my iPhone 5 and the both offered about the same protection. I don't have experience with cases for the new iPhone since i got a Note 4 this time but I read some reviews and heard the spigen cases didn't have much of a lip on the front where the speck cases did.
I have a speck candyshell grip on my Note 4 and couldn't be happier.