Assuming that we are talking about deep sky imaging, I would think that the most important consideration would be what it does to your imaging scale and field of view.
Going from an 8" F/10 to either a 10" or 11" while staying at F/10 will reduce your field of view significantly. The same chance will not significantly impact your imaging exposure times, since that's mainly driven by focal ratio.
Carolinaskies has a good table of the important numbers. On his list of scopes, the only scope that really makes sense to me (in terms of light gathering) is the 10" F/8 Meade, and then only by a minor amount. Beyond light gathering, none of the scope listed are going to have a meaningful increase in resolving power, because they are all going to be seeing limited in practical terms. The RASA scopes will offer a very significant reduction in exposure times, but they are wide field instruments - and if you want a similar effect, the cheapest option would be to get a Hyperstar lens for your existing C8.
Personally, unless you are doing planetary imaging from a site with exceptional seeing, I would not spend the money to move from an 8" SCT to any other SCT. There just aren't any practical advantages. If you didn't already have an 8" SCT, I would suggest either the Meade ACF (I would choose an 8" F/10 over a 10" F/8, unless you have a pretty stout mount) or a EdgeHD 8. But the reason for this has nothing to do with aperture. It's for other features like a better corrected field, better mirror locks, etc.
I'll note that this is not a hypothetical question for me. A few years ago, I did purchase an SCT exclusively for imaging. I have a mount that can easily carry any commercially available SCT (it'll actually carry up to a 24" R/C). Of all the available options, I chose the EdgeHD 8 and added the F/7 focal reducer, and I am very happy with that choice. I did own a Meade 8" ACF scope in the past, and that was also an excellent imaging scope. I also have a C14 and have imaged with it. But for deep sky imaging at a site with less than exception seeing, it just doesn't offer any improvements that make it worth dealing with the size and weight over the 8" (but it makes an exceptional visual instrument or planetary imaging instrument).