The question is not "which is more valuable", it is "which is cooler". Creepers are, in my opinion, cooler, because they walk, explode, grief you, etc. While diamonds CAN make the best tools, they can't walk, explode, or grief you. Think about it. Which would you rather stick in a glass box for your "TV"? A immobile diamond, or a explody-goes-boom creeper?
Creepers do have better drops. I know I use diamonds to make tools but rarely armor. I use iron for that. You can use gunpowder to make traps, TNT. IF you get a skeleton to kill a creeper then you get a music disk. (Even though I have no clue how to make a Jukebox lol) Creepers may scare the crap out of you but diamonds are more dangerous. Especially since they are normally found near lava. If you fall in lava you can never get your stuff back. If your blown up by a creeper (as long as another creeper doesn't blow it up) you can find your stuff.
Creepers drop gunpowder, which can be used to make TNT. TNT can explode like creepers. You can also make traps out of gunpowder. The only use of diamonds is to make diamond tools like weapons, axes, armor, etc. But people mainly use iron as their resource. Iron is more common than diamond. Also, you can lose diamonds to creepers, which is bad. It matters less if you lose iron, since its more common. Did I mention creepers go boom?
You can argue you can drop diamonds in lava and watch they burn, but creepers are amazing! They make holes in the ground! They stalk you through windows! They wait behind tree until you turn away and then boom! Surprise explosion!
I do not get how you can't love them. They like to spawn in groups, then forming a line and taking turns exploding until they kill you.
What makes them even better, is that they love spawning near you when you are carefully maneuvering near lava, and pushing you well into it after you mined that vein of diamonds.
I mean: can diamonds do this? No!
Lately these creepers have been stalking me. I find diamond in a deep cave, but I don't have an iron pickaxe. So I build a furnace and start cooking iron ingots. Just as I'm in my crafting table making my pickaxe, a creeper manages to blow up and destroy all of my diamond. I officially hate creepers, because even when I kill them, they don't drop anything
In a Vechs map (Also known as super hostile; the hardest maps in the history of maps and it's a CTM map; the first of it's kind), creepers are one of the most devastating mobs ever. 1. When they blow up, they blow up your stuff too. 2. Creepers don't burn in daytime, so you can't just wait for daytime and then walk around watching gunpowder deposit in your inventory. Next: Why diamonds are awesome.
1. Best possible material; as in, items made out of this material has the most durability, destroys blocks the quickest (sometimes gold is faster, but its low durability makes it impractical), and deals the most damage.
2. Required in a Vechs map for you to craft a diamond block.
3. Without a diamond pick, you can't make an enhantment table. You can make a nether portal though. In fact, you can even do it without ever mining iron!
4. Without diamonds, the achivement "Overkill" is impossible in an ordinary minecraft, no maps/mods.
So hate creepers, love diamonds!