The latency numbers show us where the 850 Pro 2TB falls short and where the 850 EVO 2TB turns into a beast. Under heavy load, Samsung's 850 Pro 2TB took nearly twice as long to complete the tests as the 850 Pro 1TB. When the drives are given time to recover, the 850 Pro 2TB fails to clean the NAND or direct the data writes to clean flash. This is something Samsung will need to look into and fix in a future firmware update.
The 850 EVO 2TB performs better than we expected under demanding conditions, and then brings the service times down to class-leading levels when it's given time to recover.