The larger model is a better deal as it’s not only bigger but comes with a transducer. They’re probably clearing them out because that transducer was superseded about a year ago but that GT54 is pretty good on a lake.
https://www.cabelas.ca/product/13690...riantId=355067
I’ve got the 10” 105sv echomap ultra paired with a GT51 transducer and have been very happy with it here on the big pond.