Re-roll or Disenchant?

If you don't want it it doesn't matter, but keep in mind that higher priced shards have absolutely no bearing on the reroll (ex. rerolling White Mage Veigar/Assassin Master Yi/Golden Alistar is the same as rerolling DJ Sona/Pulsefire Ezreal/Spirit Guard Udyr). If you need essence, disenchant the higher ones and use the lower ones for rerolls.

If you ever might want PF Ez in the future you'll want to save it of course. Also remember that sometimes Riot does 'Legendary chain mystery skins' where if you get a Legendary+ you'll get a free Mystery skin. Even if you don't want a particular Legendary/Ultimate you can craft those at that time to get free skins.

if you dont own him keep him if you do own him then disenchant him

disenchant and hard craft only. (for maximum efficiency)

if you reroll you are just burning potential dust.

the only situation where you would want to reroll is if you are looking for one skin in particular or nothing at all