As a long time Minecraft player, one thing that has bothered me for some time has been the moral dilemma of mining instead of spelunking. Why is it a moral dilemma? Mainly because I can't help wondering which way Notch originally intended players to play. Now I'm not saying that either method is wrong or worse than the other; they both have their advantages. So let's get these pros and cons out of the way and then tackle the moral ****.
+Safer than spelunking by far
+Can strip large areas of all their resources without fail
-Boring and monotonous
-Not as time-efficient as cave-diving
-Potentially thwarted by natural structures like lava lakes, caves, ravines, or abandoned mine shafts
+Get more resources than mining in a much shorter time
+Higher chance of finding rare things like dungeons, strongholds, and slimes
-Danger of dying and losing all items, undoing all the work you've done
-Risk of getting lost on your way back home
Minecraft comes with randomly generated caves that are filled with resources. With that apparent, is it wrong to assume that Notch intended for players to spelunk? In fact, spelunking is more fun than mining and yields more resources over the same period of time. To counter-balance this, monsters and abandoned mine shafts were implemented to make spelunking dangerous and fun... now compare that to the tedium of mining through thousands of blocks of stone just to get a few measly diamonds. Clearly when Notch designed the game mechanics, he intended for players to run through dark caves fending off enemies, all while in the search for those useful little nuggets of ore. Were that not the case, caves wouldn't randomly generate at all, and you'd spend the majority of your time playing Minecraft shattering your stone pickaxes while trying to uncover a few blocks of iron.
Think back to the first time you found diamonds: if you're like me, you found them deep in a cavern with lava in sight. Remember the joy you felt? As if your hard work had paid off? As if all that excitement had come to a climax and you were going to build a diamond pickaxe and kick the universe's ass? Now imagine that same scenario, but this time you found them while branch mining. Not the same, is it? Mining is cold and impersonal, and the resources you find while doing so lose this air of importance, probably due to the fact that when you branch mine, the question isn't "if". It's "when". You also miss out on a lot of the game when you mine. You don't fight anything. There's no excitement. No fear of loss. In a lot of ways, mining instead of spelunking is equal to paying prostitutes for sex instead of scoring with some hot chick at a party. With paying (mining), there is no possibility of failure, but afterwards you still might be unfulfilled. If you score (spelunking) you took a risk, it paid off, and you feel like a boss. Really, what's the purpose of all that diamond you mined? Why do you need a full set of diamond armor if you're going to spend the rest of your Minecraft life running through tunnels of your own making? Caves are there for a reason; they're fun to be in and they add to the game. Don't see them as incredibly large veins of air you bump into while trying to get a few more pieces of gold ore.
In summation, whatever you like is up to you. If you're a thrill-seeker, you'd prefer spelunking. But others prefer a nice, stable grind, and that's perfectly fine with me. At the risk of sounding corny, you can play however you want... because this is MINEcraft.
I quarry, which is as interesting as spelunking.
Why? It may be cold and impersonal, but, it is addicting, and you often strike caves full of ores.
And then you get lost spelunking.
Quarrying is almost like building. I've dug an 8x8 quarry in my current world. It was tedious and I didn't find much resources, save for the stone I'm going to build a castle out of, but I look back at the hole I dug and think "**** yeah. A lot of effort went into that. And it looks badass."
It's like mining, but also like building. The main difference is that you can look back at a quarry and think it looks impressive, as compared to looking back at a series of branch tunnels and seeing only areas that are now worthless because they have no more resources.
Oh, there's also Inventory Editing, when you're lazy (when I want to do some Redstone, I don't really want to dig it all up)
There really isn't much reason to INVedit your redstone. In one cave trip I came home with four stacks of the stuff. That'll be enough to last me through all the redstone projects I'll make for the rest of the game.
How is Mining thwarted by Ravines and Abandoned mines? I, for one, LOVE to run into these whilst mining.
If you're mining and suddenly you hit something that ISN'T stone, the miner who hates spelunking will instinctively turn in a different direction. If every direction leads to more cave, the mining operation is halted.
I find just as much victory in finding diamonds mining, as I feel like the calculating and reasoning I put behind mining is then rewarded. This doesn't mean I don't like spelunking though, as I treat it in the same sort of calculated way. I feel, for me, they work different parts of my brain and solve for different fun equations.
I generally live in ravines. Days of caving to make the place safe nets a boat load of ore and the odd dungeon. Then I take a few days to make the place accessible with stairs and bridges and end up uncovering more goodies. After that, branch mining at the bottom of a ravine is like a vacation.
+Get more resources than mining in a much shorter time
I'm not sure if you knew this or not, but ores generate before caves. Caves basically generate around the ores, hence the reason you find so many veins when spelunking. As a bit of a downside though, caves actually cut through ore veins, reducing their size. This might not seem like a lot, but it is possible for entire veins to be destroyed by caves. This issue does not exist when mining (ever wonder why you find such massive veins of diamond when mining rather than spelunking) so therefore this point is easily arguable.
When it comes to diamonds, since they are found at levels 0-16, and caves almost never go that low, branch mining at 16-0 will be the best way to get diamonds.
However when it comes to iron, the best bet is probably splunking.
spelunking is pure adventure where mining is work but pays off. I go spelunking way more often then I mine. and I tend to fall into lava more while mining rather then spelunking. (I sometimes remove that one block under me which leads to lava lol :\ )
There's nothing like the thrill of spending thirty minutes building, mining, and fighting your way to the diamond at the end of the cave. There's also no feeling equivilent to running from skeleton arrows, cave spiders, and creepers.
I absolutely love spelunking. It can make you extremely happy, and then within a matter of seconds, scared for your life. The randomness of what you find is the beauty of it really.