I love under 510. The Performance Stretch pants are the first pair of pants I have had in my life, that fit perfectly off the shelf. They are light, stretchy, and stylish. And are holding up very well in a shvitzy season, and staying strong through frequent washing.
I purchased the The Lightweight Stretch Chino looking for a little more casual look, and while i am super impressed with the material and make quality (they really are an amazing stretchy breathable stylish pant), I did find that the Chino runs slightly smaller than the Performance pants.