As a rule of thumb anything that will support my life (BCD, Reg, computer, mask, main light) I buy from the scuba experts at my LDS. Anything that is a commodity item (weights, knife, backup light, tank, gloves, fins) I may buy from the local discount store or on-line with the kid who just graduated High School and knows scuba has something to do with water, if the price is better. But if the price is close I always support my LDS, unless they don’t carry a certain brand that I really want.