Beguiler vs "Avenger"

[Killer Angel]

I am looking to play in a level 10 campaign with a few friends... I was going to play as a Grey-Elf that was a guerrilla fighter in defense of his homeland during the most recent war

I was wondering, from a strict mechanics perspective, who would make a better guerrilla fighter... I am thinking the Avenger because I can assassinate sentries and be somewhat helpful in combat (other than being a buff bot), with the low level enchantment and illusion spells to grant me the opportunity to ambush unsuspecting targets.

Where a beguiler could easily infiltrate a compound and slit someone's throat in the middle of the night, sabotage equipment and "Brainwash" people with a small amount of time and little resistance.

For classic guerrilla (hit and run, sabotage, vanish before enemy reacts), beguiler is slightly better.
But you were defending your homeland. Avenger has a name that suits better.