You have alot of options here, and how you fish would play a major part. First of all, i think 1- $300 unit is better than 2- $150 units. If you have/fish from a bow mounted trolling motor, that's where i would mount the transducer. It's where you spend the most of your day, and with a better sonar, it will help you fish more efficiently. With lake maps available for public lakes (in mi. anyways) you can still guesstimate the areas you want to fish, put the motor down, turn on the sonar and get to catching. That's how i would do it.