What are the main differences between the cast and forged lowers on AR's. Will one outlast the other and are there any disadvantages to each one. Thanks

i cant remember which one does it but sometimes the mag wont slid into the magwell like its supposed to...  i remember this from awhile back in the magazines forum... not 100% sure if this is true or not.. just what i heard

The main difference is that a forging is inherently stronger.  In the last 5 years or so, casting has come a long ways.

Now, is a casting strong enough?  Probably.  It depends on a lot of things like how the rifle is used and how the casting was performed.

The correctness of the dimensions probably won't be directly related to the base material.  It has a lot more to do with the company who made it.  Every company puts out sub-par stuff, even Colt.  You can never be sure an AR lower is in spec until you either measure it or swap some parts in/on it.

If you can wear out an AR lower, you're a brute.