Marriott is the king of market segmentation; this is one of many examples in the company.

JW's have a bit more upscale finishes (stone, tile, carpet, wood, etc.) and I believe that they all have spas IIRC.

Before the acquisition of Ritz-Carlton, I believe that JW was meant to directly compete with RC. But once RC was acquired, it obviated that market need.

Now, I think that JWs are probably built in market locations where the research shows that you can sustain a higher ADR than you would normally get with an MHRS property.