I have the Bontrager's but had to use the Ultegra's in a pinch (long story). In my brief experience with the ultegra's (a week with 500 miles & climbing) the Bontrager's were stronger to me. Both would lock the wheels so they both did their job. It's just the Bontrager's didn't require as much effort - at least my perception. FWIW they were used on the same bike, same wheels - carbon clinchers. I weigh about 60-62kg.