First, having a Pantone solid uncoated formula guide by hand, I would say that the upper (duller) color looks closer to the sample than the bottom one. But actually both of your screenshots look quite far from the truth (the 485U sample looks darker and more to the brown, and 299U looks even less vibrant).
I've converted 485U into RGB in Photoshop and it gave me #c66753, and 299U gave #548cd3, which is much closer to what I see.
Second, and more important, it's an extemely bad idea to design for screen using the PMS color specifications. Here's why.
The Pantone Matching System you are referring to has been designed specifically for print. The number of the color (without a letter index) does not actually specify the color itself as we see it - it specifies the coloring properties of the pigment used in printing. The actual color you get on a printed material will differ greatly depending on the paper characteristics. For this reason there are letter indices: C for Coated, M for Matte, U for Uncoated - to have a screen estimation of how the printed material will look like.
In your case, you have “U” colors. You would expect any U color to be rather dull because it imitates the pigment being printed on a paper with high soaking ability.
Converting a PMS number to RGB value (which you actually need for screen design) is not unambiguous. It depends on the software (proved above with CS5/CS6 difference) and active CMYK and RGB profiles used in your color settings. That's why you can use PMS number only as a very rough reference when designing for screen.
The best thing you can do in your situation is to find a printed Pantone solid uncoated formula guide and compare what you see with the available variants.