I may be a bit of a Xatu fanboy since the GSC days (I also love Espeon but Xatu is 101% cooler), but I find it to be much more useful than Espeon for a single reason: recovery. Espeon has none of it, while Xatu has Roost. I find the support Xatu gives, adding its Ground immunity and 4x Fight resistance, much better than Espeon's offensive prowess: I can kill Ice Beam-less Tyranitar with Xatu if I want to; with Espeon, I will merely cripple him before dying horribly.
And again, Ground immunity and 4x Fight resistance means Xatu switches in much easier than Espeon. It can also kill Ferrothorn easier as it resists Power Whip and takes less damage from Gyro Ball and frankly, as awesome as both pokémon are, the main reason I use them in my teams is to bounce off Taunt and hazards so, if Xatu can kill the main Spikers/SRers, I'm fine. Besides, I fucking hate Breloom, so it's a bonus.
And thank you :) I'm glad to know I was a reason for you to sign-up, I actually like your posts too.