5mm lead, 600 RPM, 600 x 5 = 3000 mm/min = 118 IPM
10mm lead, 236 IPM
20mm lead, 472 IPM
IMO, your choice is between 10mm and 20mm. It depends on the weight of the moving parts and the acceleration you want as to which one is better. Definitely do not use 5 mm on a machine with a 1.8m or 6' ball screw.