im going to have to go ahead and disagree with everyone else and say Nick Johnson. the AVG right now is bad at .135 AVG but he has .375 OBP. the AVG will improve.
Davis is young and has potential, but still his first time in the majors and i wouldnt be surprised to see some struggles.
once Johnson does get going hes going to help in R batting infront of Teixeira/ARod/Cano/ect. as LH in Yankee Stadium i think hes going to have 20+ HR.
there is always the injury risk for Johnson too.
Davis might have a higher ceiling in the future, but im just not sure i see that for this season.
i think either one are good. Davis has more potential. ohnson might be safer, but could be a risk to stay healthy.
hope i could have helped some.