1st -
- because it has a lot of creatures that go with other elements, making for cool decks. Water-poison, water-aether (kinda), water-air, mono-water... last i knew, during the war teams would lose cards, messing up a few decks etc. but when water has so many possible combos, that will make it easier for them. Also, they have lots of creature control, with flooding, freeze, infection, lobotomize, etc.
2nd -
- They have lots of creatures, all of which are reasonable in most decks involving gravity. This means that even when they lose some good cards they can still make decent decks
3rd -
- it has control and speed and can work reasonably with other elements (golem, graviton fire-eater, fractal/phoenix, immolation giving all quantum types, etc.)
4th -
- reasonable, hard to kill creatures (burrow/high hp), works in combination with some other elements (fire, darkness, time), has some control and good shields (2 damage reduction can be amazing with all unupped cards)
5th -
- has some control and works well with some elements, but it doesn't have many unupped hard-hitters
6th -
- has some control, can work well with some elements (life, darkness, time (fate eggs), mutation rainbow)
then i'll go with