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Well, reading eyepiece forums might lead you to believe there are vast differences in the quality of eyepieces in the center 25% of the field, and there just aren't.
I've owned over 300 different eyepieces through the years, and when the seeing was superb I was wowed by all but 3 of them and one of them was defective.
The point is, you won't see HUGE differences in the center of any functioning eyepiece in your scope (unless the eyepiece has poor color correction, like a Huygens).
At f/5, the differences that matter are:
--astigmatism in the outer 25% of the field
--field curvature that makes stars slightly out of focus at the edge when the center is focused.
--scattered light from bright objects outside the field of view caused by inadequate suppression of internal reflections
--differences in rectilinear and angular magnification distortions in the outer areas of the field
--light drop off at the edge (vignetting)
--overall shrpness of the star images (mostly in outer field)
--rendition of color, like a better revelation of red tints in nebulae, or a whiter image when the viewed object is white (e.g. Saturn's rings, certain lunar features)
--superior control of exit pupil aberrations
I could go on and on. The gist of it is that nearly all the differences show up in the outer 50% of the field, and not in the center 50%.
And last, an f/5 scope that is not using a coma corrector will also reveal substantial coma in the outer field. That's the optics, not the eyepiece, but it will be seen more easily in wider apparent fields.
So do you need the more expensive eyepieces to have a good time observing? No, of course not.
But for the outer 50% of the field? We have a saying: Wide field, inexpensive, well-corrected: Pick any two.
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