I stick to 5 Enhancement Shaman, with the Earth Elemental you have a Pockettank whenever you need. The instant heals are great and there are some nice Azerite Traits for more surviveability.
5 Elemental Shamans might be stronger because of the ability to power up their Elementals, for M+ it is nice to have. Maybe 4 Elemental Shaman + Heal.