I had exactly the same dilema and actually ended up with both.
So this won't help very much. The ease of use of the Garmin is superb with its touch screen BUT the Structure Scan is pretty impressive too.
I've not been using mine (Structure Scan) for very long but it performed pretty well on its first outing looking for an 11m fishing vessel sunk in 25m when searching on a sea running a moderate swell. (That said the Lowrance is refusing to power up so far after the winter break but I'm hoping that's just a bad connection)
The Garmin so far has been faultless. I'm running fuel flow sensors on that too which seem to be pretty accurate so far.