Go for Gen3!
The Gen2 units is the older model; can't update them using wifi. Also, the chart update rate is just too slow compared to the Gen3; drives me batty when trying to find the structure - after locating with my sidescan on the Gen3 console unit.
I've got both a Gen2 (bow/TM, sonar only) and Gen3 (console with sidescan) networked with my Xi5, and I am constantly frustrated with the update rate on my Gen2 - which is the bow unit connected to the Xi5. When I connect the Gen3 to the Xi5 - all issues disappear! Lots of talking with Lowrance, while on the water, to try and resolve, but they can't help! Says it is cause of the older unit.