Bare EQ Magnum heads vs. machining stock Magnums?

TrailBeast said
That's what I did (CH318B)
The EQ's are thicker cast where the stock magnums tend to crack.
Every once in awhile you hear about the crack allowing a valve seat to fall out either hanging the valve open to the point the piston hits it, or breaking up and trashing the piston, cylinder AND the head.

How's that for a good feeling about the EQ's?:D

I have heard a lot about stock Magnums cracking, seems like it's mostly minor though is it really that common for the seats to just fall out?

Also are the stock valves really that bad? What's wrong with them? I don't want to have to get new ones of those too if I can. .