It all depends on your components. In general if you want to run Multi-GPU water cooling is preferred, as more often than not, the top GPU will suck heat from the bottom one, and with water cooling this isn't an issue.
In some configurations air cooling can be fine too, but it's always best to have custom cooled video cards with a spare/empty PCI-E slot in between them to avoid this scenario.
Since TT now makes some epic water cooling cases now, and if they are your preferred case vendor, then it's a no-brainer.
I have a Core V1 and V31 and the V1 with a small mod (cutting the mobo tray) can hold a massive, front-mounted 200mm radiator, and the V31 can actually hold two 360mm radiators, which is amazing for this size of case.