I have both, and I like them both. VAMO is longer and heavier, but you can use it in 18350 mode, although with the VAMO I have to use a 510 to ego adapter to run T2's and T3's. The Sig ZMax is a nice device, not quite as tall and lighter, you can run T2's and T3's without an adapter, it has the one button menu system, so not quite as easy to adjust voltage/watts.
If it comes down to price, VAMO wins, not sure how many VV/VW mods you have, but if you are like many of us you will end up with more than one. I have five, counting the spinner. Good chance that which ever one you chose, eventually you will end up with both.
I actually use all mine in rotation, different delivery systems, different juices, don't have to constantly change delivery systems.