After my OnGuard Pitbull Mini fell off my bike the rubber cracked off of the lock and I decided I was done with OnGuard. It was scary to see how much bigger the rubber made the lock look. Kryptonite is more expensive but I think they are stronger locks & worth the extra money. My NewYork STD U-Lock I bought for $56 seems very strong against manual attacks. I can't imagine twisting the shackle to defeat it would work. The steel seems like a higher grade & I'm pretty happy. I live in Chicago so I need a strong lock. Bike theft seems really bad this summer. Although I suppose a angle grinder or chainsaw that the bike thief pros use would cut it? Thinking about adding the BikeRegistry chain lock to my defense as well.