I could be wrong, but it's my understanding the AV's have leaf springs in the erector assembly. The Z3's have multiple radial coil springs instead. Again, I could be wrong.
I have several AV's and a couple of Z3's. A couple of the AV's have suffered the dreaded POA/POI shift. Swarovski repaired them as usual with their MOST EXCELLENT customer service.
When I purchased my first Swarovski I actually wanted the fixed power. But, it was more expensive than the variables. Given their track record with customer service I took my chances on the variable. They haven't been trouble free but, once repaired, they work fine.
