Some caveats: I haven't played 6E yet, nor am I privy to any insider information.
That said, as I've been listening and reading between the lines, I've feel like I've heard few things from the devs:
1) In 5E, armor had inflated so much that it devalued Body. If everyone is running around with 12 points of armor from an armor jacket, why bother with anything more than Body 3? Spending finite attribute points in Body generally wasn't a good investment, since the % change to your soak pool was so small. The optimal approach was the maximize Intuition and Reaction, not only because they were tied to useful skills (unlike Body) but also because they were superior to Body in terms of reducing damage and/or avoiding it altogether. So, the new system is to intended to rebalance the importance of Body.
2) The high armor values of 5E lead to high weapon DVs which often lead to dodge-or-die situations. Some devs like this and some devs don't, citing realism or game balance to support their preference. The new system is intended to make things more granular so that a single hit - or a single poor soak roll - isn't an automatic death sentence.
3) Similar to the above, a high base DV devalues the net hits that a skilled attacker can adds to the final DV. Take the FN HAR for example. If your base DV is 10P (in 5E), the difference between 1 net hit and 3 was modest from a % lift standpoint (since 13P is 18% higher than 11P), but if your base DV is 5P (as in 6E) then the lift is much more significant (8P is 33% higher than 6P). So the new system is intended to make your skill more important not just for determining whether you hit or not, but also how well you hit and how effective it is.
Again, much of this is based off asides and me reading between the lines, so don't take it as gospel. I'm not saying that I agree with it or that I would have done it the same way, but that's my current understanding behind the changes in 6E's approach to armor, Body, and weapon DVs.
This is not the ideal takeaway for the effects of 5e armor.
For example, high body is pretty meta among soak tanks due to the interplay of soak and edge. It doesn't make sense to pump body too hard if your not going soak tank, this is true, but body and strength are really strong on soak tanks in 5e. The stat definitely had its place.
5e was a significant DOWNGRADE of lethality from 4e, where it wasn't so much 'dodge or die' as 'Have 40 soak or die' because the final DVs of weapons in SR4 was
higher than in 5e.
For example, a Machine pistol in SR4 had a BASE DV of 4, but a final DV of 13 (lets forget about ammo and assume this is a cruddy ganger with an MP). Your armored jacket negated 3 DV. If you didn't have pretty much every soak aug in SR4's core book or a troll's body, you couldn't survive that damage, so the smallest gun in the game that isn't a single shot gun, something any idiot could get for the same price and avail as a handgun, would kill almost every SR PC pretty much automatically. In SR5, you only break DVs of 13 on really big guns like shotguns and sniper rifles. So survivability in SR5 is much higher, especially because in SR4 the way defense was calculated made dodging weapons impossible. So even the weakest autofire weapon in the game would kill any PC besides a street samurai hit by it nearly 100% of the time. For reference, the Panther was 10 DV.
SR5 was probably the least soak minmaxing intensive edition of SR printed due to the fact base armor was really good. It is super incorrect to state that it was more lethal than previous editions where your soak 6 body 4 armor was going up against someone firing 3 hypervelocity submachinegun shots at you for 16 DV 3 times, all shots being made with a pool of 12 or more against a defense pool of... reaction alone. Unless you full defensed in which case you only got to add 1-4 to the roll.
Obviously, this environment where you auto-hit reduced the importance of skill dice even more than 5e. In fact, in SR5, skill dice are hugely important due to the relationship between DV and autofire now: Higher dice isn't an efficient way to get DV directly, but it indirectly increases your DV because semi-auto and single shot weapons tend to hit harder than the burst fire or autofire they lost would negate in defensive hits. In fact, in SR5, despite the increase to soak, most of your lost DV as an attacker doesn't come from soak, but from defense dice, even vs grunts who aren't optimizing for it but have the good core rules armor, which is why for most PCs automatic weapons were still the ideal: Yes that sniper hit WAY harder than the AR (rather than way less like in SR4, where machine pistols hit harder than a panther...) but if your missing 35% of your shots your way better off with the AR. This also really hurt 4e's balance, because the nominal cost of autofire (recoil, which in theory lowered hit rate) didn't matter because A: You got more dice from gear than you do now, and B: Even on a full defense test your rolling like 8 defense dice optimistically, and full defense was just a terrible deal vs ranged weapons as it guaranteed you would get shot an extra time.
In fact SR5 probably had the best balance of defense vs offense of any SR edition, because its totally possible to go into combat as a non-soak tank and eat a few shots and not die, but it is still rewarding to really push that soak up because really big scary guns still exist, and it is still possible to achieve the classic samurai trope of bullet immunity. What SR5 did was heavily squeeze the range of DVs down, increased base soak numbers, and removed the insane impact autofire had on DV, resulting in damage generally being very consistent and PCs fully capable of surviving attacks from even serious guns rather consistently, but making it possible to get unlucky on either side of the attack. In SR4, a light pistol failed to do any damage through an armored jacket worn with a helmet while a machine pistol without special ammo would consistently kill a body 5 reflexes 4 character through full body armor 80% of the time, and your survival rate vs an assault rifle with ExExplosive is 4% with FBA.
This actually had huge ramifications going from 4e to 5e, mainly the fact that armor was no longer virtually worthless made it so PCs who weren't soak-stacking could participate in combat without instantly being popped the second the standard PR1 Halloweener grunt took out their TMP with their 6 attack dice and got even slightly lucky on the attack, forget about Corpsec utterly annihilating you with an HK-277. You get shot in SR4, you best be a samurai, be getting hit with a 'toy gun' in single shot or semi-auto, or be a soak tank samurai limb build.
