i got 5 gallon pots only because my local hydro store was out of 3 gallon.... lot of people say go with 3 gallon which i would take that advice cause i just did a major flush and flushing 5 gallon pots are a bitch cause you gotta run 15 gallons of water through em..... i would say if your growing indica go with 3 gallon and if your growing sativa go with 5 gallon. thats my $0.02