Hi M.-

I vote for personal preference.

Every adjustment you make in the way you hold the guitar, for instance:

*sitting on the couch
*sitting on a chair
*sitting on a tall stool,
*standing up, with the strap attached at the juncture of the body and the neck of the guitar,
*standing up, with the strap attached near the nut of the guitar,
*holding the guitar behind your head (just kidding)

Every adjustment you make in the way you hold the guitar has an effect on the angles at which your each of your hands approach the instrument. Try a few different configurations, and you'll see what I mean. Some positions make it easier to see, some positions make it easier to strum with power, some postions make it easier to reach certain extreme chord positions...

In other words, personal preference.

But preferably, personal preference determined after checking out a variety of options and really tuning your attention in to which position allows you to play your best in the style that you are working on.

-Lisa