According to the DH errate vs 3.0 that was put out there are NO differences between swift attack and lightning attack...OOPS on company part. The following are direct excerpts from the errata file.
Lightning Attack on page 117 should include the
additions: “If you have the Two-Weapon Wielder talent
and are wielding two melee weapons, you get the advantage of
Lightning Attack with only one of the weapons, and a single attack
with the other. If you have the Two-Weapon Wielder talent and are
wielding a melee weapon in one hand and a pistol in the other, you
get the advantage of Lightning Attack with the melee weapon and
a single attack with the pistol.
Swift Attack on page 122 should include the addition “If you
have the Two-Weapon Wielder talent and are wielding two melee
weapons, you get the advantage of Swift Attack with only one
of the weapons, and a single attack with the other. If you have
the Two-Weapon Wielder talent and are wielding a melee weapon
in one hand and a pistol in the other, you get the advantage of
Swift Attack with the melee weapon and a single attack with the
pistol."
That is just lazy on someones part....they copied pasted and just changed the words ( swift attack / lightning attack) for eachother with no actual difference between them. Tsk Tsk
House rules for the games I run are simple fixes for this...
Swift attack - same as listed ( 2 attacks with first weapon and one with second if dual weilding w/appropriate talent )
Lightning attack-( since its SUPPOSED to be better than swift it is)-It gives 2 attacks with BOTH weapons ( if dual weilding w/appropriate talent)
)