Here is the list of players in both the NES and Arcade version, I did quickly so correct if necessary, listed by Arcade team:
Houston (11)
Cruz
GDavis
Walling
Ashby
Thon
Doran
Bass
Hatcher
Puhl
Ryan
Scott
Oak (3)
Reggie
Canseco
McGwire
Atl (1)
Dale Murphy
Chc (3)
Sandberg
Dawson
Sutcliffe
LA (4)
Guerrero
Lopes
Sutton
Fernando
STL (6)
JClark
OSmith
Coleman
Mcgee
Tudor
Worell
SF (1)
WClark
Cincy (0)
Boston (5)
Burleson
Boggs
Rice
Evans
Clemens
NYY (2)
Mattingly
Righetti
So by my count there are 36 players in both versions. A total of 160*2=320 players less 36 duplicates, so 284 unique players.