The higher the objective the better light gathering in low light situations. The bigger the objective the bigger the bell and higher rings needed. Like JLS stated this becomes a cheek weld problem unless you have a add on cheek piece or a higher comb stock. I have scopes with both objectives but on all my standard rifle I go with 40 or 44 mm objectives because good glass helps with with light transmission and the lower rings help with cheek weld and instant target acquisition.