Arguably the best BMX bikes ever created were made in the late 80's from HUTCH. The very best model had a magnesium frame and forks. As well as Magnesium hubs with Titanium axles.. These bike were super light and beautiful to ride. Magnesium is lighter and stronger than Titanium. The biggest benefit is that magnesium flexes. This is a major plus and the secret behind the beautiful smooth ride. Where the stiffness was needed such as the hubs than Titanium was used for the axles. Smart eh! I have been waiting for someone to start producing Magnesium frames again. Now the bad part. Yes the Magnesium Hutches did have a tenancy to crack. I'd still buy one and they are worth more today than they were new.
Hope this helps