Rust vs Salem
Rust
Rust is hardcore survival game where the only aim for every player in the game is to survive. Being a survival game, your character will have needs that you'll need to fulfill or risk getting ill or worse... dying from it. There are tons of recipes for you to craft a wide variety of items from as long as you've got the resources you need, and you can also hunt and built a shelter.As fun as this game may sound, the community in this game can be a bit toxic. Most players have a kill-on-sight policy (even if you're naked and literally have nothing with you) and this means playing alone can be very frustrating. If you're planning to play this game, you might want to get a larger group of friends - maybe somewhere around 5 or more players - or you'll quickly realize you want your money back now.
Salem
Salem is an old-school and somewhat obscure (but fun) sandbox MMORPG that unlike Wurm Online has a stronger emphasis on its in-depth crafting system and survival aspect rather than building.Similar to Wurm Online though, Salem is not a voxel-based game, but you are still able to mold the game environment through resource gathering, mining and digging in a way that reminds me of the currently-shelved MMORPG, EverQuest Next: Landmark. Of course, although not exactly the focus of the game, you can still build your homestead and the process is quite similar to Wurm Online except that it occurs at a much higher speed.
Not to mention, the game world in Salem is simply humongous to the point where it feels like an actual world. Salem also borrowed some features from ArcheAge where open-world PvP is the norm, so you'll need to be vigilant at all times, but players who kill and steal for no reason will be labelled as criminals and can be punished.
However, as good as it is despite being an indie MMO and all, Salem does have its fair share of flaws due to its low development budget. So, we'd recommend you to take a look at Salem without carrying along any high expectations. It's a pretty good MMORPG like Minecraft, but if you're expecting a Minecraft clone, you may end up disappointing yourself.