You should decide on the tank first cause both those tanks i would light a little differently. If it were me, i would spring for the larger tank, the extra depth and volume will go a long way when your aquascaping. T5ho's will give you a better, and more even spread of light with less spillover, you also have a ton a bulb's to choose from to get the look you want. Take a look at the ATI dimmable 36x4watt. these are expensive, but the ability to dim the fixture, ramp up the c02 and lighting in unison, is well worth the money. If your gonna go high tech, might as well go all out. Another thing worth looking into is a wet/dry sump. If you plan to go high light, the wet dry will give your tank much more 02, allowing you to run the c02 at higher levels safely.