NavList:

There have been a few great replies to this thread and all have pretty durned good information.  I will add a small bit - I prefer to have a wider field of view since it makes it easier to find a star and hold it while bringing it down to the horizon.  This is useful for quickly shooting a star that has not been pre-planned ahead of time.  I'm more of a periscopic aviation sextant user where I preplan the shot with Pub249v1 well before going out - if you are outside, you have a lot of stars as available targets and I find it's just easier to pick a visible star, invert the sextant, and bring the star down to the horizon.  And as I am rather clumsy, I find the 4x easier to manage.  That's just me - others more coordinated than I am may be just fine doing this with an 8x inverting telescope.

If you are doing lunars, on the other hand, higher magnification is useful.