Not very experienced here, but I say find one with a style/look you really like and then research that model to ensure it's up the level of quality and capabilities you are looking for. The Zmax was my first APV and I love it. Smaller than I anticipated but every bit the power house I had hoped for. Recently bought a K100 mech mod and love that one too, though it took more work figuring things out than with the Zmax.
Other mech mods I tend to favor:
-
sigelei #19 and #20
-K101
Other VV/VW
devices:
-Vamo
Edit: If this is a first APV, I would definitely recommend a VV/VW
device before a mechanical. If for no other reason than the ohms and voltage readings a Zmax or Vamo offers.