I'm really not sure it's 50%, but I'll take your word for it until I can get around to looking it up. If that is true, it is an advantage: But it's also very much a materials-progress thing - I honestly don't need more brightness/vibrant-ness than my N900 screen puts out - but even so, the better materials can be manufactured, the more resistive screens can be made to filter out less light.
If it's questionable, then it's not really there, now is it. It's possibly there. I mean, if that's an 'advantage', then you can CHOOSE to use your fingers on a resistive screen. I rarely ever use the stylus - for precision presses, the callouses on my fingers and/or fingernails are 99% enough. And already that's more precision than a capacitive screen gives you, with the same 'soft' surfaces. Then if you want, yes, you can break out the harder pens/styli. But I don't see how that's a capacitive advantage, when a quality resistive screen doesn't actually stop you from using touch.

This reminds me of this anecdote I read by some jeweler, who was ranting about how people have this irrational expectation that diamonds can't be cracked by impacts against hard surfaces.

There's a major difference between hardness of the type that has to do with bending, and the hardness that has to do with scratching. From a scientific perspective, they're two different things and actually DON'T have to correlate. A diamond might be the hardest substance known (other than what happens if you compress or molecularly rearrange diamonds, in which case you get even harder diamonds that can't be scratched by normal diamonds, but whatever).

Anyway, you could actually have a flexible surface that is also very scratch resistant. It hasn't been done, but it's not like there aren't improvements in that area. At the same time, the aforementioned thing about microscratches screwing up conductivity of the capacitive screen decreasing accuracy is just as much of an issue. One's just less visible, so we ignore it, because that's how humans work.

Also, now that I think about it, with stantum's spacer dots idea, the fact that you could probably decrease distance between screen layers even more would presumably mean that you can opt for somewhat harder (as in scratch resistant) materials, and not loose sensitivity. (If I'm actually right about the spacer dots enabling smaller gaps. Logically it makes sense to me, but I may be missing some key aspect of the problem, due to lack of any real experience in the subject.)

Isn't the whole point of this thread Stantum screens, which do the same?

Not really trying to rag on you specifically, or rejecting that capacitive has advantages - though more and more I'm arguing that modern technology means the advantages of capacitive screens are rapidly withering away.