You could be right. I should know but I don't. When I did a head to head, side by side comparison of the GT15 and the TM150 I found no difference.
I'm very reluctant to say one transducer is better than another without looking that them both showing the same things at the same time. I've pulled the GT50 off the boat as I just don't see the same usefulness of side imaging as others being that I use the PS30. In the spring when our fish are shallow I do find side imaging very useful for showing me fish that even the PS30 misses because of its dead spot at the top of the water column. I have not found any brand to be better than another for showing me spring crappie from 0-30 feet whether roaming, near structure or on banks. That includes Hbird compact SI xd, LSS1, and the Garmin GT's. I just picked up a SonarHub with LSS2 xd off ebay for a song and I'll be trying it next spring.