These two machines are, for all intents and purposes, the same. When 3D Systems bought ZCorp they took the Z650, slapped a 3DS logo and some different colored plastic on it, and called it the Projet 660pro.
Starting with an empty machine, it will cost about $9,000 in initial materials just to begin printing, and I’d recommend having additional on-hand so that you can replenish as needed and reduce downtime. If the machines will be seeing pretty heavy, (ie. production level), use, I’d recommend investing in the extended parts warranty since some of the most common parts replaced can cost upwards of $1,000. If you want more specific information let me know.