They have their differences. I've had 3 World blocks. One blew up worse than anything I have seen N/A. It didn't have anything to do with the block but it did. One I have have now and it has 5 rebuilds on it and has been flawless. The other is steel and not valid for this thread.
The World used to come already with bushed lifter bores, pushrod oiling, clearanced for 4.5 stroke, and outside of a little grinding for pushrod clearance is ready to go save the deck checking, mocking up, etc.
The Indy is all about upgrades and is hard to get to the lifter as there are only small holes for the oil to drain back. It may be stronger though.
That's my opinion, I've had 2 KB's too and would rather have one of those, but that's for another thread.