Minecraft wiki entry for Things_not_to_do, associated text: Iron tools are faster than stone and have almost twice the durability of stone tools. Weapon damage is greater and armor can be created from this material. Iron ore is fairly common but not unlimited. Iron ingots can be infinitely acquired through an iron golem farm. These should be most player's go-to tools for traveling or adventuring.
Diamond tools are for special missions where the player wants stuff without having to create large numbers of tools and work fast. However, the supply of diamonds is strictly limited, so the player should choose carefully how they use and risk them. Given that the player should try to get the most out of their diamond items, they should enchant their diamond tools with higher enchantments.
Shovels also get used up, but are much cheaper than other tools, only one diamond piece is consumed. If the player has many diamonds, an "eternal-shovel" may be a decent time-saver.
Swords only cost two diamonds and can give the player a key edge in fights, making them more worthwhile for everyday use by the player, but the player should also remember that the more expensive item also increases the possible cost if the player does die.
Diamond armor should be carefully thought about by the player, as the player could lose a high investment (24 diamonds for a full set of armor) if they die. Just with diamond swords, the player does have higher chances of survival while using these items which makes this a real decision.
A diamond hoe is mostly useless as it deals almost no extra damage compared to fists and there are no special enchantments for it. (however as of 1.16 hoes can receive the enchantments all other tools can receive.) Hoes also always till farmland instantly, making the only advantage of more expensive hoes being long durability and slightly faster breaking times on certain blocks. This decision should be weighed against the choice of using those same diamonds for another tool or a sword. Diamond hoes are only worth the value if obtained from a toolsmith villager because a diamond is far more valuable than 2 emeralds.
Netherite is more powerful and durable than diamond, but also much more expensive. Upgrading a single diamond item to netherite requires four pieces of ancient debris, which is extremely rare and difficult to get without blast-mining, and four gold ingots to craft a netherite ingot, added to the resources necessary to acquire the diamond item. Repairing the item without Mending costs an additional 4 ancient debris and 4 gold ingots at least, and a matching item at most. Tools, weapons, and armor of this tier should be saved for difficult battles or large projects rather than worn away gradually on resource gathering or chores.