Actually every Eevee evolution has advantages and disadvantages. It's just what you want to have and focus on.
If you want a more tanky character Espeon isn't going to work indeed specially on lower levels. But that isn't where espeon is builded for.
Espeon stats on sp.atk/speed are really really strong, these are the only stats that matter for the pokemon to start with. Espeon isn't going to tank a lot of dmg, because its job is to start the fight and finish your oponent off with a hard hit right out of the gate.
For example: a level 35 espeon has about the same or even more sp.atk then gyarados that is lvl 55, or a lvl 45 espeon has more sp.atk then typhlosion at 60 or it has even more sp.atk then legendary lugia 10 levels under it.
It's fast, and its strong.
My skill setup on espeon is atm this ( lvl 71 ):
1) shadow ball ( i have it to kill other psychic pokemon with ) it 1 hits them easily as its a ghost attack
2) psychic ( your strongest attack by far, this just destroys every pokemon you throw at it with the stats espeon has, if it doesn't it lowers the sp.def and will even hit more harder the next round )
3) Grass knot ( the issue with shadow ball and psychic is, that it doesn't work well against water type / rock ones etc, this skill only does with espeon weight limit 60 dmg, but because of the high sp.atk and a lot of pp usages its incredible effective against those pokemons and a must in the build.
4)morning sun ( lvl 71 skill ) it heals your espeon for 50% which gives it survival if its needed. The only downsize is it's a late level skill.
You can solve issue's with fire / steel / electric types by replacing morning sun skill 4 with dig. It's super effective against that if you even had issue's to start with. i found out that psychic pretty much one hits fire/electric anyway.
Besides this Espeon has one of the best ability's:
Espeon ability = passes a burn, poison or paralysis to the foe. which in my opinion is a really really good add that prevents your espeon from falling behind when you didn't 1 hitted a enemy.
Specially the paralysis part is really handy, as it slows your first movement down through reduction on speed. Instead of falling behind by having to use a paralize cure and getting dmg without doing dmg that round, or fall behind in speed it automatically pushes the enemy with the same disadvantage which still gives you the edge. the burn/and poison are just bonusses.
I myself choice for espeon in soul silver, the reason for this is in short:
1) It's sp.atk + speed are ridicilous high.
2) yes alakhazam is probably better