Grilamid (polyamide) is a popular choice for touring boots because it shaves significant weight off your feet—something you'll really appreciate on long uphill climbs. If you're primarily skinning and skiing backcountry, that weight savings can make a noticeable difference in your energy and comfort over a full day.
The trade-off is that Grilamid can stiffen up noticeably in extreme cold (below about -15°C), which affects how the boot flexes and responds. It's also slightly less durable than polyurethane over the long haul. For pure resort skiing, traditional PU shells still offer more consistent performance and better longevity.
So if you're logging serious vert in the backcountry and weight matters, Grilamid is absolutely worth it. Just keep the cold-weather limitation in mind if you frequently ski in frigid conditions.