Bigger is better, no doubt about it. I started with a 55, moved to a 65, now I have a custom built 170 gallon (60"x30"x24") with an eighty gallon sump/refugium. Each time I was amazed at the extra room I now had. I was convinced that it would take a long time to fill them up. Well, time can be shortened with some cash and fast growing corals. I had to let my giga clam go because it grew to big in only 1 ½ years, almost 15" long and 8" wide.
I plan on a new house in about two years and it will have a least a 300 gallon tank.
I know it is a big jump in $$$ for a really large tank. It will cost you more in the long run though to start small and then upgrade. Buy the biggest system you can fit and afford
Here are a few shots showing how fast one can fill up even a large tank
March 1999, just after set up
October 2000
There are more in-between shots
here.
The only time I would say smaller is better would be in reference to propagation tanks. Shallow tanks with a large system volume are the way to go here.
[ October 10, 2001: Message edited by: THillson ]