I've been asking myself the same question as of late. Below are where my thoughts have landed after some research:
If you go the non-EdgeHD route, the corrected image circle is extremely small. You will 100% need a corrector/reducer such as the starizona sct corrector/reducer, or the Celestron corrector/reducer for imaging on a non-EdgeHD SCT. This will give you better star shapes across the image and lower focal ratio, which is helpful with regard to total integration time. However it also reduces the focal length of the scope, so resolving some of the smaller, more distant galaxies would be tough. Furthermore, you can't really image DSOs with good results at its native focal length.
With the EdgeHD scope, it is field corrected by default, so you can image at the native focal length with great results. You can also get the Celestron EdgeHD reducer and image at the reduced focal length as well, which is a nice bonus if you need a wider field of view.
From that perspective, (having two focal lengths with corrected fields instead of of 1), I think the EdgeHD version of the scope makes the stronger case for imaging because of the additional corrected field at the native focal length, which the non-EdgeHD scope does not have.
Presumably, both could also be fitted with the starizona hyperstar, which would add another field of view for both, but that's more useful for imaging nebulae or other DSOs that appear larger in the sky.
That said, if you'd be happy utilizing a single focal length that can still do a great job capturing lots of galaxies, saving some money on the 9.25 XLT is certainly worthwhile, and plenty of people do it. You could also get slightly better results with the 9.25XLT over the 8EdgeHD if you ever wanted to try planetary imaging as well. Don't forget to factor in the cost of the reducer/corrector on the 9.25XLT for your comparison though!
Either way you go, you can still achieve some nice results.
CS
