Certainly because of the metal, Al is more prone to cracking from damage than cast iron. But, unless a valve hits a piston, you really overheat the engine or improperly torque the head it is really unlikely that you will have any problems.
While cast iron heads can handle more heat, Al displaces heat easier allowing higher CR and ignition timing...fyi
I've heard of stock cast iron 289 heads cracking more often than aftermarket aluminum heads. I have two cracked 289 heads right now. Now, if the Chinese start making a rip-off copy of the Edelbrock Performer heads, the story may change.
The buggers are already making a cheap knock-off of Edelbrocks Performer RPM Air Gap intake - but it says MADE IN CHINA on the bottom in big letters. Yikes! get it away!
Aluminum heads also take about 50 pounds off your front end
Right you are. For me, they helped mitigate the weight increase when going from 289/302 combos to the W, although not entirely. Car gained around 60 lbs from the engine and another 50 from having to add more struts to the roll cage to meet specs. Not much on a stocker but when the car weighs 2300 wet it does make a difference. CG shifted a little back due to the weight distribution so I had to change the instant center location slightly on the 4 link.