Idunno, they made two equivalent models of computation. I think that Alan's discrete computational model is more useful for programmable computers, Alonzo's is more useful for FPGAs and circuitry. Alan just turned out to have the model which was most amenable to direct mapping of a stored-program computer. If you want to run Alonzo's model on a stored program computer, you need a compiler. And to do it efficiently, you need a better compiler than has ever been devised.