Spaarti Clones were the clones created for the Imperial Empire, due to the Kamino Rebellion killing most of the Kaminoan cloning scientists.
Due to the death of many experienced Kaminoan scientists and the Kaminoan rebellion, the Empire had chosen a new producer for clones in order to make an army for the Empire. Emperor Palpatine had chosen Spaarti scientists, as they could create a fully mature clone within a standard year, as opposed to the standard 10 years it took to a clone to fully mature on Kamino.
However, these new clones were not superior to the original 501st clones. The Spaarti had recieved flash training, which only taught them the basics of being a soldier, such as how to fire a rifle. They did not go to cover when fired at, and had notably poor accuracy, as noted by members of Omega Squad. Along with this, they did not know anything of Mandalorian tradition, which was taught to every original Kaminoan clone.