The old adage was always low frequency longer range, higher frequency better target definition. And yes beam width makes a difference, much like if you took two flashlights out and one had a concentrated beam, the other a wider beam. With the same power you would see farther with the concentrated beam, but a lot more with a wide beam. In sonars that is directivity index. Pretty easy to see that transmission power is only part of the equation, but easy to understand and measure so usally a major part of any sales pitch. Power output, frequency,directivity index and receiver sensitivity all are factors. While not as big a factor in low power units, the ocean environment plays a huge role in military grade sonars. As such they adjust power,frequency, pulse length etc to get the best results.
It's hard to get a lot of the technical info and sometimes it's of dubious quality. I think the best thing is to poll the users, which is why these forums are great.