I think first thing is to compare the world race block to the indy block. Although it doesn't change much in the strength factor it has some better options like bushed lifter bores and dual bell housing bolt patterns. Indy has a larger skirt and the fifth main is cross bolted.
Some peoples opinion may be the indy block is stronger but unless you were in the design room it's only speculation. Looks can be deceiving. Something like the quality of the block material can throw that theory out the window
Most will never run either block close to their limits