I wanted a quiet(er) system that looked good, and after seeing Liquid_Cooled's PC, I knew I wanted DD 
I ended up with a TDX, Maze4 GPU, Eheim 1048, and a BIP2, which gives me silence and good performance (Sub 90F idle, sub 95 F full load) with my overclock (2500+ mobile @ 2.4GHz, a 600 MHz overclock).
To each his own I guess, but my system allows me to have MUCH higher performance if I wanted (New pump, and turn my fans up).
I used 3/8" for my first build, but next time it's gonna be 1/2" or 7/16", simply because I like the look of the fat cooling hoses going everywhere
I ended up with a TDX, Maze4 GPU, Eheim 1048, and a BIP2, which gives me silence and good performance (Sub 90F idle, sub 95 F full load) with my overclock (2500+ mobile @ 2.4GHz, a 600 MHz overclock).
To each his own I guess, but my system allows me to have MUCH higher performance if I wanted (New pump, and turn my fans up).
I used 3/8" for my first build, but next time it's gonna be 1/2" or 7/16", simply because I like the look of the fat cooling hoses going everywhere