Rome total war or Medieval 2?

I want to buy either rtw or m2tw for my laptop. I have got the demos for both games and they both work. However, whearas i can run rtw on full settings, to play m2tw i have to turn the settings to their lowest. I am much more interested in medieval time period so i would prefer m2tw but i think maybe i should get rtw because it works well. Whats your opinion on each game and which do you think i should get?