on the def vs arm matter, there's some shifty and misleading stuff going around with the values for two reasons:

Reason the first:

We're operating on something that resemblesnormal distribution. (2d6 is actually triangular, but bear with me.)

(courtesy of Mit.edu)

The takeaway here is that stepstowardthe mean become progressively more impactful, stepsawayare progressively less.

Example:You're RAT 7, shooting a DEF 10 target. You need 3s to hit. The likelihood of you hitting is 97.22% If we change this model to be DEF11, you'll hit 91.67% of the time. That one point of defense is worth 5.55%. Same target, but it's got concealment. 5's to hit, you're hitting 83.33% of the time. While just going up to DEF 11 is worth 5.55, going up to DEF 12 is a whole 13.89% increase in miss rate (Meaning that the second point of DEF was worth 8.34%). Same attacker, same defender, butcover? 7s to hit, hitting 58.33% of the time. Cover increases the miss rate by 38.89%, meaning that the third and fourth points of DEF are worth 25%

Same shooter,muchmore slippery target. DEF 14 base. Hitting 58.33% of the time. One point nets you 16.66% additional survivability- pretty serious. Concealment gets you up to DEF16, which takes 9s to hit, you're hitting 27.78% of the time. It's rare, but it's less significant an accuracy hit than going to DEF15, as it only adds 13.89% to the miss rate (Concealment is worth 30.55% here) . DEF18 takes 11s to hit, 8.33% chance, so while cover on a DEF 14 model vs RAT7 strips away a whopping 50% of the hit rate, the third and fourth point are worthlessthan the first two you get from concealment.

As shown, every step away from 2d6=7 is less meaningful than the last, and every step towards 2d6=7 is conversely more meaningful.

_{Addendum: RAT7 is used because it represents both "accurate" guns and "average" guns aiming.. that and it hits DEF10 on 3s, unlike RAT6 or RAT5. }

How does this impact armor?

ARM values comfortably go higher, but so do POW/P+S values. This impact is a lot more evident on single wound models like infantry, asanysuccess leads to a disabled model, whereas multi-wound models also measuredegrees of success. It'd take a lot more math to determine whether or not the impact is greater on multi-wound models than on single-wound models.

Since POW7 isnotthe measuring stick of weapons, we need to shift the distribution over a few points. If POW 10 is considered the "baseline", as we'd done with RAT 7, then ARM 13 is equivalent in value to DEF 10, ARM 15 to DEF 12, and ARM 17 equivalent to DEF 14. Extending to 2d6=1 and 2d6=13, ARM values cease to match with DEF, as DEF0 is missed by a roll of 2, and DEF100 is hit with a roll of 12. ARM0 is damaged by any roll, and ARM100 damaged by no rolls at all.

Reason the second:

Conditional defensive benefits do not have equivalent conditional armor benefits. Conditional damage benefits do not have equivalent accuracy benefits.

In short: Concealment, Cover, Elevation, and attacking over an obstacle exist. These give bonuses to DEF based on terrain. Charging gives boosted Damage rolls outside of Focus/Fury manipulation or special rules. No such universal rule grants boosted accuracy, save for aiming.

tl;dr DEF and ARM of equal value are not of equal value. in a RAT7 POW 10 world, ARM provides as much protection as 3 points less of DEF. Numbers courtesy of http://anydice.com/program/a5e8

Addendum to tl;dr: In a RATXPOWYworld, ARM provides as much protection as (Y-X) points less of DEF