All at full power
Element four - Phantom lord
Sound 4 - orochimaru
Sound 4 can use all forms
Sound 4 includes Kidomaru and Element 4 includes Gajeel
Sound 4 with Kimimaro? and Element 4 with Gajeel?
Sol and that Fire mage wasn't that impressive. In fact I dare say they are weaker than Jirobo the weakest Sound 4 member However, Current Juvia and Current Gajeel are much stronger than before.
If Element 4 wins considerably its only because of Current Juvia and Current Gajeel had future panel time for their feats while the rest of Sound 4 with Kimimaro died in part 1.
element four would likely win due to their superior haxness
Only the Airspace user's magic, and Juvia's water prison are hax. The other two element 4 weren't that great.
Sound 4's hax included the
Jirobo's Draining Chakra Earthdome, His CS2 strength >> element 4's physical strength
Tayuya's Demonic Flute and Doki summons who eat up chakra.
Sakon/Ukon split and Cellular deconstruction
Kidomaru's Durable elastic webbing + his CS2.
However Juvia and Gajeel current feats (due to them having panel time) should be suffice.