When powered by similiar engines these aircraft had similiar performance. If anything the Do-317 looks a bit superior. 406mph. Ju-288C. 3,000kg bomb bay. DB610 engines. 416mph. Do-317B. Essentially a Do-217 with larger DB610 engines. 2,500kg or 4,000kg bomb bay. .....The version with larger bomb bay carried less fuel. January 1941. Ju-288 prototype first flight. By this date the Do-217 was entering operational service. Test pilots reported the Do-217 performed well even when powered by 1,100hp DB601A and 1,200hp Jumo211B engines. It appears to me the Luftwaffe just didn't like Dornier. Why else would they spend money to develop the Ju-288 and Fw-191 airframes when the Do-217 airframe had already proven itself and was already in production?