Like Thumper said, where the applications are is paramount. Mag tends to burn in powder form and even at times in sheet form. It can also tear. Yes, it is much lighter but rather unpredictable, so be careful when trying to weld it.
I would not trust it in certain applications even though Funny cars have used them in the past for one or two passes in a season for each part I suspect. I was at once thinking of using it for my interior door panels and such, but after seeing its characteristics in a fire, I decided against it.
Titanium has been proven to be super strong for certain parts.

Titanium has been around in race cars for some time now and nothing to do with imposter/wannabe's out there today, but Apollo Trick Titanium, a company once based in Troy Michigan had worked closely with Chrysler during the early 70's in their Motown Missile Drag programs.
I do concur that Mag is a beautiful metal along with Titanium.