It really depends on what string you're coming from. It makes sense to bend the strings nearest the fretboard edge away from the edge, but for the other strings, the only thing you need to take into account is what string you're coming from, what string you'll be going to & the bend hits the right note.
For example, if you're playing the A string & want to bend a note on the D string, then it makes sense to bend the string away from the A string. Then if you're playing the G string & want to bend a note on the D string, it makes sense to bend the string towards the A string. Though this depends on where your next note is going to be.