It just depends on the type of world you want to create. According to the wiki there is always a chance for it to set on decay.
Most the worlds I created at random always seemed to have a bad combination of negative effects. Of the two crafted worlds I made on the server I just picked a series of biomes and crystal and glowstone as well as villages and strongholds. It came out nice.
Each time I crafted a world it added some random effects I didn't pick. Like one came charged with constant lightning storms.
I think if I'm allowed to make another one for the server someday might do a cave world as that's pretty cool.
One of the stable worlds I made I picked flat. Flat for Myst world makes ground level fill all the way up to cloud level. So clouds become a type of fog on the world. the down side is minerals still spawn at normal depth, so have to dig way down to get to them.
Playing: Minecraft, Tera Online