Hi, Chief
Only "real" difference lies in the layout of the beam and poises:
5-0-2 has two poises. One on left moves in 5 gr increments. One on right moves in full gr and 1/10 gr increments at the same time, e.g. 1 gr, 1.1 gr, etc., up to 5 gr.
5-0-5 has three poises. One on left moves in 10 gr increments. Middle one moves in full gr increments, up to 10 gr, one on right in 1/10 gr increments up to 1 gr.
Neither is "better" or more accurate or any of that. 5-0-2 is (perhaps arguably?) "easier" to use. Many of us have had 5-0-5s for so long we don't notice the extra step...
Rick C