Yes, you are correct and cast rotors also do crack, they just generally last longer than 'drilled' rotors. Porsche has specs for this, that any crack greater than 7mm in length or is near the edge of the rotor and it is toast.
Cracking generally is an issue that occurs under extreme use, such as hard racing conditions which most of our trail and road machines will not see.
You can also get rotors that have been cryogenically treated which is supposed to increase their durability and longevity.

Personally to me if you live in a flat area where you are not potentially overheating your rotors up stopping a heavy rig, then go with stock replacement, probaly cheaper in the long run. If you live in a mountainous area and are frequently stopping or using brakes alot on downhill descents where they can heat up stopping a heavy rig on oversized tires, then give it a try.
In my experience, it does help with brake fade and so far have had no issues with longevity.

 

DBA Disc Brakes Australia is what I plan to use when the time comes, the slotted ones (T3) seem to do well.

 

Mark,
I know of one lady that did that, oversized rotors and six piston calipers, bigger wheels and tires. She says she has better stopping power.
They look good, but she doesn't off road...should work very well though.