yes splitting up into 2 cpus is no fun either , its a lot of work and cost either way, using EMb looks easier to implements if the codeing can be done ok , another issues is the amount of i/o ports the emb takes ,

the i/o ports cant really be used for anything else except the eMB bus, cos even if the ports / normal cpu i/o while not using the emb , any code that runs in the emb and requests hardware connected to pins that are emb bus wont work