The Nilas is quite a bit lighter than the Peak XV (22oz versus 34.6oz), due in part to a lighter shell fabric (15d versus 22d). Both have a fair amount of pockets, but I'd give the nod to the Nilas for having the more useful assortment of pockets for backcountry use (2 handwarmer + 2 interior water bottle pockets) compared to the Peak XV (2 handwarmer, 1 chest, 1 interior chest). Both combine 850FP down with baffled construction, but given the overall weights of each garment, I assume that the Peak XV has a greater fill weight and overall loft, and would be warmer as a result. I can't really say how much warmer because neither EB or MH provide total fill weight.
But if I had to guess (based on shell fabric weight, number of pockets/zippers), fill weight for the Nilas is probably close to 9oz, and the fill weight for the Peak XV is probably around 15oz.
Edit: I was wrong about fill weight for the Peak XV, apparently fill weight is close to 13oz, according to the following thread, that is (see eric chan's post):