Dean, it is not lost on me that those extra three or four pounds for a large chuck pale in comparison to the stress of roughing an unbalanced 20-pound piece. I figure a more massive chuck will always add a certain ratio of wear and tear; as I said there is no free lunch. I could have been more succinct with the question and asked if the extra wear and tear from adding any extra mass to the spindle would be a linear ratio, which I expect and can live with, or if there was something unknown to me (and so much is, you know) that would cause more of an exponential effect.
It is not linear, however, it is actually two curves since the extra kilo of mass would be there the whole time the chuck is in use, while the unbalanced 20-pounder only spends a portion of its time in that state, and ought to become a better-balanced 16-pound piece right away. If your point is that I'm splitting hairs, then yes, probably, but I didn't know that for sure when I asked.

So I might have been surprised to learn that the benefits of the flywheel forces due to the extra mass (including the intangible extra safety it may add) is orders of magnitude greater than the constant wear from the extra mass, so much so that not only would a larger chuck not hurt the lathe, it actually adds life to the bearings in the long run. I dunno, but it sound like I shouldn't worry about the constant wear from the extra mass. "Don't worry about it" works for me.
Gerald, one thing I have been looking at is whether the chuck is one of the few that are available in "native" 1.25"x8tpi format or uses an insert like most do. I liked the T40 because it already has a large spindle and move-up issues are not as great, if they ever arise at all. All other things being equal, to my mind there is more advantage to the native threaded design, since it removes an intervening part and all of the subtle inaccuracy and potential failure points that accompany each additional component in a system. If I have to use a spindle adapter later, that's fine perhaps, but I would like to have that be the exception, not the rule. I realize I might not get my wishes granted on this one, but it would easily break a tie for first place.
Seth, I am really diggin' the Easy Wood chuck now, in spite of the auto-panic that Robo Hippy set off with the "p" word. What I hate, hate, hate, specifically are set screws and that dumbest of all fastener engagement methods: the hex socket and key. It find it a bit oxymoronic (like jumbo shrimp, or "large Midi") that they would abolish the evil eight set screws and then turn around and use a hex socket and key for the final jaw tightening. My drill chuck is keyless, so what's the problem with going keyless on these chucks? I am looking at all of the vendors here, not just Easy Wood. I have to assume there is a good reason nobody has a hand-tightened 4-jaw chuck. But, but, how often will I change jaws? That, I do not know, and there's the rub,since I don't know that yet. I might spend the next year doing 700 8" bowls and never needing anything but #2-esque jaws.
I think I could get past the hex socket for the jaw change advantage of Easy Wood, although here again, I will be tightening the jaws far more often than changing them. The price of a C2000 stings rather much; I don't have a per-item budget, I have a global one where I skimped on disposable or more easily replaceable items like chisels and grinder wheels to pay for higher-end big ticket items like the lathe, grinder, and a starter chuck. That budget is nearly exhausted, and Easy asks for a pretty big premium even over the other high-end chucks -- they want my vari-grind and a hundred bucks instead of me just buying a OW or similar. So, how much is my time worth? I didn't dive into this whole thing to waste time fiddling around and cross-threading set screws. The little video of the jaw change with the chuck on the lathe is really enticing, though. Over a long period, even if I value my time very little, the chuck pays for itself, premium and all. I am looking at the jaw options now but I am having a little trouble finding the jaw sets for sale, but I am sure they're out there.
I should probably start compiling a list of things I like and do not. Unfortunately I will have some time to do this before making my decision. I don't really have any time to even scratch myself, with my current life obligations and still needing to outfit the shop, build a bench for the lathe and all of that. This somehow gives me a sad period of time before I get to turn anything.
These are all very useful answers, thanks for chiming in.