Duergar immunities or stubborn?

[James Gibbons]

I'm going to be playing a duergar archer ranger in an upcoming game set in the underdark. Rangers have good fort and reflex saves and poor will saves. My wisdom will probably top out at 14, currently 13.
I'm wondering if I should switch duergar immunities

Spoiler:

Duergar Immunities: Duergar are immune to paralysis, phantasms, and poison. They gain a +2 racial bonus on saves against spells and spell-like abilities.

For the stubborn dwarf trait

Spoiler:

Dwarves are renowned for their stubbornness. Dwarves with this racial trait receive a +2 racial bonus on Will saves to resist spells and spell-like abilities of the enchantment (charm) and enchantment (compulsion) schools. In addition, if they fail such a save, they receive another save 1 round later to prematurely end the effect (assuming it has a duration greater than 1 round). This second save is made at the same DC as the first. If the dwarf has a similar ability from another source (such as a rogue's slippery mind), he can only use one of these abilities per round, but he can try the other on the second round if the first reroll ability fails. This racial trait replaces hardy.

using the dwarf traits option

Since I'm going archery I won't have any extra feats to spare I won't be getting iron will. I think this option will offset my poor will saves. I may also get the birthmark faith trait for another +2 vs charm and compulsion

[James Gibbons]

Deffinitely taking birthmark.

[Dave Justus]

The more situational a bonus is, the less I like it. Partly because they apply less often, but also because I am more likely to forget about them when they do apply. That would make me prefer immunities, even if it wasn't as good of a bonus to the more narrow stubborn.

In this case though, I can't see why you would possibly prefer stubborn to Immunities. The only thing that stubborn gives you is a reroll. Even without the immune to paralysis, phantasms and poison, +2 against all spells and spell-likes beats the heck out of +2 only against charm and compulsion.

[James Gibbons]

The reason I would prefer it is because having me firing arrows at my team mates for even one round is much more lethal to the party than being paralized. On the other hand drow use a lot of poisons. Poisons are fortitude though which I have good saves on. However spells covers almost everything.
I've heard will saves are most important though

[Rynjin]

Immunity to three things and +2 to nearly all saves trumps +2 to nearly all saves and a re-roll any day.