I'm using a 5-gallon orange cooler at present. I'm thinking of moving to a rectangular Coleman Xtreme cooler (blue, of course)--probably when summer ends and the home improvement stores put things on sale. I routinely brew small batches for a variety of reasons (space, only beer drinker in home, etc.). I rarely brew above 7% ABV.
I'm thinking a 36-quart cooler would be plenty for my needs, and that anything larger might work against me (more surface space = more cooling). Thoughts?
The big reasons for eventually moving to a rectangular cooler are that it would be less awkward and to provide a more even (and more efficient?) mash bed.