Everyone loves Espeon :L
Anyway though Espeon may be the more offensive Magic Bouncer what does it honestly have over Xatu? You see Xatu may not boast the pretty decent SAtk and Speed Espeon has but it is slightly bulkier and has some very nice resistances that would normally just screw Espeon over. The added electric, Ice and Rock weakness is maybe a little unfortunate but the main abusers (CBand Tyranitar, NP Thundurus and Mamoswine) all 1hko Espeon anyway due to its medicore Def allowing any Pokemon to really screw it over. The flying type Xatu boasts allows it loose its weakness to U-turn and Grass moves. This is very important. In a world where Breloom is a massive threat one quick prediction on the opponents part could easily result in death for Espeon with a single Bullet seed doing about 60% with a possible 4 more to come. This is where that extra Def comes in. It just helps it switch in on Ferrothorn and others incredibly well while taking minimum damage. When it does take damage it can roost right back up with its decent speed. Which brings me to my next two points. Though Espeon does have recovery can you rely on it to waste a turn (with its poor defense) using Morning sun which in a tier where Sand and Rain are the only types of teams you will ever see. Though Espeon does have the better speed stat, you need to ask yourself is it needed? Everything that sets up par lead Terrakion is usually running more than 218 Speed. Even then Xatu has Thunder Wave which is great support and lets it Roost first for some serious trolling. Finally we come to Espeons SAtk. It is pretty impressive though in the modern meta it can't really abuse it as if you want to make the most out of your Espeon you need to run max investment in HP and run support moves like dual screens as everything practically 1hkos it. Using an offensive set is a bad idea and can lead to certain death. Overall Xatu actually can run a pretty nice semi offensive pivot with Twave, Uturn, Night Shade/Psyshock and Heat wave actually making it the more offensive of the two.
So basically that's my opinion as currently I believe Xatu has a better niche than Espeon in Ou, both offensively and defensibly while offering nice support. Though who you choose should honestly depend on your team as a more offensive team would likely benefit from paralyses and U-turn though a more defensive team would probably benefit from Dual screens if you can be bothered to set them up.
@ Leftovers
Trait: Magic Bounce
EVs: 248 HP / 204 Def / 56 Spd
Bold Nature (+Def, -Atk)
-Thunder Wave
-U-turn
-Roost
-Heat Wave
