I remember reading back in the day (when PoP was new), the low 60s Monster Summoning (V I think it was) was a good pet (probably the best), but that was short-lived.
As a tank, I prefer the Air pet for the stuns, they lower the mobs dps, help interrupt spells, can tank if need be, and are ok DPS. If you get good at positioning the Water pet would probably be better for a high dps, low mob difficulty group, but in general, I'm with Cilrail and say Air pet. Octavia's mage primarily uses the Air pet as well for both soloing and grouping.
Yther Ore.