OLOF mostly contains translations by Anglo-Catholics associated with the Oxford Movement, and that bias frequently shows up. ANF/NPNF was translated by Protestants, although in some cases a high-church Anglican bias is still evident. Both series have some unevenness in the quality of the translation of various works, including places where a fairly "loose," almost paraphrastic method was used. In occasionally comparing both versions with the original Latin or Greek, I find I sometimes prefer the renderings of one over the other. But then, that result is probably a reflection of my own limitations and biases...