Hi, Matt - I downloaded your files and was able to open them without any problem.
It turns out that the two jpgs that you enclosed were in different color spaces. The file labeled as "...too dark" was in Adobe RGB, whereas the file labeled as "...acceptable" was in sRGB. In fully ICC-compliant, color-managed browsers, there should be virtually no difference between an Adobe RGB image and the same image after being correctly converted to sRGB.
In fact, because you also enclosed your xmp file, I was able to do exactly that: I made ACR also render this image as an sRGB file, and, as expected, it looked essentially identical to your "too dark" Adobe RGB jpg. So, the "too dark" look that you don't like is clearly part and parcel of the image itself and the ACR settings that you used. This means that if you want to lift the shadows like you did, you have to do it by adjusting the RAW image in ACR. Of course, as pointed out earlier in this thread, you should never post any image on the web in anything other than sRGB, but fortunately, that's easy to do, and it looks like you already know how to do this.
The real question is whether or not you really want to lift the shadows by the amount that you did. On my hardware calibrated monitor, I prefer the version you labeled as "too dark" (which is exactly the same as what I got out of ACR). To my eye, the version you labeled as, "acceptable" looks like there is a haze permeating the darker parts of the image. However, the difference is within the bounds of personal preference, so it's a judgement call UNLESS you are not using a hardware calibrated monitor. If your monitor isn't regularly calibrated using a good quality external hardware device, I would suggest that you leave well enough alone and not try to lift the shadows because you simply can't trust any non-calibrated monitor for adjustment decisions like this.
If you want to be able to see detail in the shadows, there are other ways to achieve this without making the shadow areas look hazy, and I've attached a version below (last attachment) where I cranked up this approach to "11", LOL, to make it easily visible. Obviously, one can dial this (local contrast) effect all the way back to just lifting the shadows without introducing the more over-the-top look. See what you think. If you like this look, let me know and I'll write up what I did.
Tom
