Hi Spencer, i think i am well qualified to comment as I have had one and do have the other.
I started on the Nalu, and its was good for FW but never could get comfortable surfing it, I was always falling off due to the stability and I called it corkiness, for me it just didn't turn, but it was my first board and to the credit of the person that sold it too me, it did what i wanted got me up and catching small waves (albeit in a straight line!)
Mid last year I bought the Avanti and its a BIG board, but only when your on land, on the water, its super stable, and for the difference is that it turns, big time, so my surfing has gone forward in the last 6 months. When your on a wave if you step back you can pretty surf it like anything else as all the volume is out of the water.
The only detraction is it can be hard to get out the back at times in certain conditions.
Having come forward in surfing, i am somewhat interested to go back to the Nalu and see if my opinion has changed with my ability. But I suspect the lack of width would still cause issues in all but ideal conditions, and that could just be a me things.
I'm 115 kgs and am going to demo a couple of boards in the next week to see about going slightly shorter and narrower to overcome the getting out the back issue. Progression I think they call it!
Attached is a vid of me surfing the Avanti a couple of weeks ago (be nice it was my first vid on the GoPro!)
For your criteria, I think the Nalu would have the stability in FW with your dogs, but for my 2 cents worth the Avanti surfs better
As everyone says try and demo if you can.