I like big. mostly because of the boil over factor but also the more water you can use in the boil the less sugar concentration and less chance for scorching on the bottom. That said, something with a heavy bottom is better. I like to brew on an old wood cook stove I have in the basement (translated: man cave). The stove heats even across the whole bottom of the pan so I can use a large enamel on steel canning kettle without scorching. On a regular stove, electric or gas, I would opt for a heavy bottom stainless stock pot that will hold at least 8 qt with a head space of not less then 4 inches. For me that would be the smallest. And just remember: it will boil over, at least once. So plan on having a big sticky mess to clean up and think of it as a welcoming to the club.