What type of riding are you into? If mostly XC, I'd recommend the X517. I'm running the X317 and I'm very pleased with these as my "race" wheels.
I've always liked Mavic products, they last longer than other manuf. I've tried and are well made products.
I also have a set of D521's that I use for everyday riding. They're a little heavier, but much more durable!
I've never had any Bontrager product, but it's a well respected company.
L8R
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"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming, "WOW, What a Ride!" - unknown
"Your Bike Sucks" - Sky Yaeger