depends on what u planning to keep. for me, i will prefer 2.5ht. i prefer tank to be high as i like to c my fishes swim up n down.....i have a 6" tang inside my tank n 2.5ht is juz nice for him. if 2" then it will make the tank look shallow...of cos if possible, go for 4*2.5*2.5. can play with depth n height.