I ride over 10,000 miles a year and I've tried a lot of different bike shorts. In my opinion these are the best you can buy. They are comfortable for any kind of riding and any distance. They hold up well. I'm 5'1" about 160 pounds and I wear the xl size.
Castelli is top notch quality. My previous pair lasted 9 years. Very compressive fabric. Go up one size from what you would normally wear. They run smaller.
I have bought this short for a number of years and had to return twice. Have ordered L previously but ended up having to go to XL and then 2XL to get a proper fit.
My weight over this time has remained the same.