Eidolon with Weapons: Feat or Evolution?

[Amuny]

Hop:

Weapon Training (Ex)
An eidolon learns to use a weapon, gaining Simple Weapon Proficiency as a bonus feat. If 2 additional evolution points are spent, it gains proficiency with all martial weapons as well.

Martial Weapon Proficiency (Combat)
Choose a type of martial weapon. You understand how to use that type of martial weapon in combat.
Benefit:You make attack rolls with the selected weapon normally (without the non-proficient penalty).
Normal: When using a weapon with which you are not proficient, you take a –4 penalty on attack rolls.
Special: Barbarians, fighters, paladins, and rangers are proficient with all martial weapons. They need not select this feat.
You can gain Martial Weapon Proficiency multiple times. Each time you take the feat, it applies to a new type of weapon.

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Assuming I'm actually playing some kind of "angelic" eidolon wielding a Greatsword, and that it is the only weapon I want to use, could I just take the feat, which has absolutely no prerequisite, instead of something that actually uses 4 evolutions points? :o

[Artanthos]

I don't see why not.

The evolution is a generic ability that allows you to use a wide range of weapons. The feat is a specific ability that allows the use of a single weapon. There's not much of a conflict between the two.

[Raymond Lambert]

Also consider giving the eidolon the feat additional traits. than pick heirloom weapon(warning it has had errata) for proficiency with one weapon and another trait for whatever else. You can say that the summoner has adopted the eidolon as part of the family, maybe even being used as a substitue child after a sudden death of a child.

This would not be a good choice if you wanted an eidolon with multiple sets of arms each weilding a short sword but would work better if you only want to use a single weapon. in home campaigns, you can turn the weapon masterwork with a spell from UM so it can later be magically enchanted.