To me the argument seems to be: photographer A uses jpeg and takes really good photos. Therefore I should shoot in jpeg. The problem with the reasoning is that the reason the photos look great to you don't really have anything to do with the fact that they were shot in jpg. Framing, composition, subject, patience, lens acuity amongst many more variables are far higher up the priority list in terms of what is responsible for why the photo is likely appealing.

I can say this. There is nothing you can do with a jpg (processed by the camera's internal software) that you can't do with a RAW. But there absolutely are things you can do with a RAW image that you cannot do with a jpeg. If you've ever missed exposure by a stop or two or had auto color balance leave you with a color cast, there is no question that addressing this in post via a RAW image will result in a superior image. Or if you're shooting a scene with a large dynamic range (e.g. you'd hope to preserve detail in the sky), it makes little sense to throw away that data by immediately relegating the image to only 8-bits.

The short answer, though, is that in most applications the RAW vs. jpeg question is mostly moot. If you're close on exposure and color balance and not hoping to bring the shadows up or highlights down significantly, jpeg is just fine.