Actually, Milotic walls Way better according to stats, but there are a few things Jellicent has over it.
Being Part Ghost Jellicent has STAB Ghost moves and Access to a...
Jellicent can run some sick nasty sets, Including the ever so loved - (Willo Wisp + Hex) - combo.
Even Though Milotic Can Take Water moves Like a Boss, a Slightly Injured Jellicent Can get 1/3 of his Health back from any Water Type move, which also heals off any Stealth Rocks damage you might have taken.
Okay, this is a biggy, Normal and Fighting moves don't even Touch him, Which makes him a Great Conkeldurr switch in, With Conkeldurr being a large threat in the OU Meta Game, Jellicent can take a Fighting move with Nothing happening, and Then Willo Wisp, Recover any Coverage damage taken and Hex his Face off.
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So, As you might have seen, its not always all about stats.
My Reccomending Jellicent Moveset and Ev's Etc.
Jellicent (M) @ Leftovers
Role: Tank
Trait: Water Absorb
EVs: 132 HP / 96 Def / 120 SAtk / 160 SDef
Modest Nature (+SAtk, -Atk)
- Will-O-Wisp
- Hex
- Recover
- Surf