Largemouth are more territorial than smallmouth. In lakes where there are only smallmouth, they tend to occupy prime real estate that a largemouth normally would. There are VERY few lakes where this is the case though. When both species are present, smallies either wander, or occupy the next best location, often deeper and cooler. Some wander sop much, they key on baitfish, not structure, so you have to learn how to read super structure, and how huge schools of bait relate to it. The notion that largemouth are a larger species isn't exactly true, either. Northern largemouth bags are often overshadowed by smallmouth bags when smallmouth are accessible. On the Great Lakes, while there are smallies in the warmer protected bays, they are dominated by largemouth, while the open water lake, and it's huge schools of pelagic bait are the domain of the smallmouth. I'll tell you this much about growing up on Port Bay, Lake Ontario: while I love largemouth fishing more than just about anything, if the weather cooperated, I'd leave the bay, and look for smallies in the big lake.