From time to time, i see a real high level espeon as gym defender. They are a kind of glass cannon, but hurt a lot until defeated.
To do the pure math, Jolteon is not really worse. Slightly better on defense, considerably lower att-stat, but - better moves! VS hits harder than Confusion on defense [Correction: hits as hard, but generates much more energy, takes a bit more time, thanks to ClayMask!], Thunder Bolt hits harder than Psybeam. I expect the moves to compensate for the lower att-stat.
The interesting thing would be typing. The best type counter to Espeon would be a Bite-Trex - not everybody has it already. The best type-counter to Jolteon is Rhydon, virtually everybody has one.
But - do all attackers know and chose the correct type counters? Would they do in this case?
And the bigger Problem: Jolteon has lower CP than Espeon.
Is there anything to add to or to argue about my analysis?