I have both the RCO M4 and the TA 31F. Both fine scopes. If I had to do it over again I can't justify the big price difference between the 2, The only difference is the 5 mil horizontal stadia in the RCOM4 and for a civie like me I don't find much use for it. For the same price I bought a Nightforce 1-4X24 that has a much more useful reticle and is illuminated. Yes the fiber optic light feature on the 31F and RCOM4 is nice but I don't do any night shooting.