Most of the time when this is an issue, it would be best to use the feel of the keyboard and the feel of different intervals or jumps. Often however it is quite necessary to supervise the hands, as they are very disobedient with huge octave leaps and the like, such as at the beginning of Liszt's 1st concerto. In that example, both hands have parallel difficulties, I'm not really sure what is most "safe", nothing is really safe there, just have really solid octave hands and use your eyes, I guess. In most cases one hand clearly needs to be watched more than the other, in most of the first movement of Rach 3 this would probably be the left which jumps around all the time. I think feel is very important, if you are well centered at the first note then you might know where the next is. Don't stare at your wrist because it will cause it to explode! or at least become very tense which is also bad.
Most of the time when my hands are far apart I see the other one with sort of peripheral awareness, like you said, I don't actually look in its direction. Focus wherever it feels natural to focus, let your eyes watch whatever wants to be watched. There is no set rule, use your judgement of the context. The more important hand to focus on is the one that does worse when not watched; with chopin preludes for example, no. 3 the left hand does lots of stuff and has a huge range and lots of different hand positions, but falls in a regular pattern with no leaps; the right hand doesn't do much but you should probably watch it or you might miss the notes.
I hope this helps.