It depends on the bass...
Some basses that have smaller bodies, you shouldn't be resting your arm on the bass. In some cases the body is just too small your wrist is forced at a harsher angle.
On the Jazz Bass above, I rest on the bass.
My Ken Smiths, I rest on the bass.
My MTD535 however, my arm does NOT rest on the bass. When it does, it is uncomfortable to me. But I also use that bass mainly for Slap style...
The way my bass lays, it is kind of at a tilted up angle already.
The picture kind of exaggerates the angle of my wrist. This picture shows how it lays, although the picture is at kind of a funny angle... but I think you can get the idea...
