I prefer doing smaller batches for now. I have to brew on my stove top which takes a long time to heat 6 gallons vs a 3 gallon run. As others mentioned, you get to try new things out, get a feel for different ingredients and the flavors they impart. I would advise anyone to start washing the yeast to save $, also, try to buy some of your materials in bulk to save $ as well. I usually buy my base grain in bulk, hops in bulk and then I get to play around with specialty malts and yeast strains. I ferment in my 7 gallon buckets and if I condition, I let it sit in a smaller vessel to free up my primaries.
Although, I still do about 2 or 3, 5 gallon batches a month but the mini brews are fun to play with, IMO. Brew on!