Depends on the purpose it will be used for . Of the 3 the OBR is going to be the most accurate , easily MOA or better with good ammo . The shorter M1a's can be finicky and I wouldn't mess with one shorter than 18" , with work and good ammo you can expect 1 - 11/2 MOA . The FAL in my opinion will be the most reliable if you get the rifle length operating system , the 16" guns with the short op rod have had issues in my experience . The FAL's are going to be the hardest to shoot well as the best FAL trigger is still not close to the triggers on the other two with the OBR being the best . Both my FAL's , a full size DSA medium contour gun and Congo para rifle are 1 - 11/2 MOA with good ammo and 2 - 3 MOA with surplus depending on manufacturer .
Precision rifle get the OBR , battle rifle get the FAL .