I can not see a large sweet spot at the Kowa Genesis 8x33.
I already have a Swaro EL 8,5x42 (bought in 2009), and now bought an Kowa Genesis 8x33 for my wife. I am unimpressed with the optical quality of the Kowa. The mechanical quality is very good, just in negligible details behind the Swaro.
The first Kowa i received was noticable decentered, for trained watchers viewable less sharpness in areas on the left half of the picture. My dealer sent me a second one. Theese one is still decentered, but ist is just a slight effect and you must hard look to see it. Anyway, i do not know that of my EL.
The contrast ist sligthly worse than of the EL 8,5x42. That surprised me. Marginal less contrast causes less colour aberration. The Kowa is noticable better in colour aberration.
Resolution in the center is no difference between the Kowa and the Swaro.
The resolution (sharpness) at image borders, not just the edges, at both Kowa Genesis 8x33 begin remarkable earlier decreasing than of the EL 8,5x42. Resolution start decreasing just out of the picture center! Kowas lack of sharpness in image borders is heavy, also considered without comparison to the Swaro 8,5x42. I can not accept that in this price class. I is unbelieveable for me that other Glasses like Zeiss Victory 8x32, Swaro EL 8x32, Leica Ultravis HD 8x32 should playing on the same low level as the Kowa Genesis 8x33 here.
Regards Marsu