Well, it's Friday and I'm bored, so let me see if I can still do math:smiley:.

Your current gears give +13 to lightning skills. Assuming you also have torch, anni and 3 lightning skillers, that's +20 skills in total. Since it's a pure lightning sorc, we'll reasonably assume you've put 20 points in CB, Lightning, CL and LM (and no point in Nova yet). This gives 1~912 base lightning damage (at lvl40), +320% synerge, and +518% lightning mastery. So the total damage is (1~912) * (1+320%) * (1+518%) = (25~23671). Similarly, we can calculate that taking away one soj and adding a facet will give 1~876 base lightning damage (at lvl39), +320% synerge (no change), +506% lightning mastery, and +5% facet. So the total damage is (1~876) * (1+320%) * (1 + 506% + 5%) = (25~22479). I'll ignore the minimum damage for the rest calculations.

Now let's compute the actual damage output based on the monster resistance:

Code:

```
[FONT="Lucida Console"]Monster Resist 0 50 75 99 100 115 125
Resist With Soj -85 -35 -10 14 83 98 108
Resist With Facet -90 -40 -15 9 78 93 108
Coefficient w/ Soj 1.85 1.35 1.10 0.86 0.17 0.02 0.00
Coefficient w/ Facet 1.90 1.40 1.15 0.91 0.22 0.07 0.00[/FONT]
```

So your actual damage is multiplied by the coefficient above:

Code:

```
[FONT="Lucida Console"]Monster Resist 0 50 75 99 100 115 125
Damage w/ Soj 43791 31955 26038 20357 4024 473 0
Damage w/ Facet 42710 31470 25850 20455 4945 1573 0
Damage increase -2.47% -1.52% -0.72% 0.48% 22.89% 232.56% ---[/FONT]
```

As you can see, switching from SoJ to Facet is almost always a bad idea for monsters that are not immune to lightning. For LI monsters, however, facet is a much better choice as long as you can break the immunity with Infinity. So you should make your decision according to what areas you MF most. The Fingermage in Sanctuary and Willowisp (souls) in Throne are two most common LI kinds I think, both with 100 lightning resist in hell. Other than that, I don't think there's any major LI monsters in common MF areas, which means switch from Soj to Facet will make almost no difference in killing power (2.5% drop at most).

However, in terms of increased MF, you current gears give about 150MF as FrostBurn said, so an increase of 50MF from Occy will increase the chance of finding uniques by 9.3% and sets by 12.6% (use ATMA to verify these numbers if you want).

So this is a case where the increase of MF outshines the decrease of killing power (in case of non-CI's), and I'd say you should go for the change (assuming you can survive well in both cases).