After a fairly cursory look – admittedly more at some of the Army Lists than the rules:
1. There are provisions for the non-active side to React in both the Initiative and Command phases. Interesting idea, will have to actually play to see how it works.
2. There are no longer separate FACs. It appears FOs, previously called FAOs, now request both air and artillery. My first thought is that I am not that fond of it, as now there is no delineation between a nation's artillery support doctrine/ability and their air support doctrine/ability – beyond limits to units and overall support, and their Air Superiority rating.
3. Army Lists – the column orders are different; most notably in BkC II AT comes before AP, in BkC III, AP comes before AT. Annoying change.
4. Unit Notes/Special Abilities. In BkC II, these were in the flavor of Notes. For example, a Tiger I would have a Note # which would be "Tough: Flank hits do not reduce armor save." Now there is a Special Ability called "Good Armour", which translates to: "Units ignore the -1 save penalty for flank or rear hits." Just eye-balling it, there appear to be more Special Abilities than there used to be Notes, and seems more in the vein of FoW.
5. Oddly (to me anyway), in BkC III, the Panther has the "Good Armour" Special Ability. From what I have read, that is not warranted given the Panther's relatively thin flank/rear armor. But let's compare the Panther and the Tiger I in BkC II – BkC III (if only one value is listed, it is the same in both versions):
AFV; Move; AT; AP; CA; Hits; Save; Cost; Notes/Abilities
Panther; 25; 5/80 – 6/100; 3/80 – 3/100; 4 – 2; 6; 4+ – 5+; 215 – 190; BkC II: <none>, BkC III: Good Armour, Tank Buster*
Tiger I; 20; 5/100 – 5/100; 3/100 – 3/100; 4 – 2; 6; 4+; 230 – 165; BkC II Tough, BkC III: 1944+, Good Armour
* Tank Buster = Reduce a Hard target unit's save by -1 against hits from it's AT attacks.
Observations:
- The Panther does not have a date restriction. This is no doubt a typo, but as written the Germans can have Panthers in Barbarossa. Won't that be a shock to the Russian players!
- The Panther gets the same "Good Armour" special ability as the Tiger I, the only difference is its Save is one worse. So in BkC II, the two AFVs were equal on defense, except the Tiger I was less vulnerable from the flank/rear. In BkC III, the Tiger I is better all-around since it saves better. Seems to me BkC II is more in line with what I've read.
- The Panther's AT ability is much better in BkC III: its range is better (and the same as the Tiger I), it gets and additional attack die, and it is a "Tank Buster".
- Obviously the CA values are reduced for both. I haven't investigated to determine if that's a philosophical change in BkC III to make AFV CA less effective, or if it is offset by additional modifiers, as compared to BkC II.
6. One Note that didn't transfer is in BkC II, some AFV units, e.g. the Support Unit (IG, 150mm, Pz I) and Ferdinand, had the note "No Machine Guns: No bonus for firing at soft targets." In BkC III, there is no such equivalent Special Ability. All AFVs add +1d6 when firing at INF within 20cm. Further, in BkC II, AFVs added +1 D6 vs. [all] unarmored targets within 20cm.
7. Less units/detail: I mentioned the BkC II Support Unit (IG, 150mm, Pz I) – i.e. the SP 15cm infantry gun (Gw I), in this case mounted on the PzKw I chassis. I don't see any of those SP IGs in the BkC III lists. I also don't see the Sdkfz 250/1. On the other hand, BkC III still has the Zgkw, 88mm in the German Army, Early War, Sep' 39 – Jun '41 list, and they had what – 10 of them…
8. Less delineation in the Army lists: In BkC II, there were separate German Early East Front, Mid Eastern Front and Late Eastern Front lists. In BkC III, there is one German Army, Eastern Front, June '41 to May '45 list. One difference in BkC II was the Mid Eastern Front list had the aforementioned Ferdinand, while the Late Eastern Front list has the Elephant – which does not have the Note about lacking MGs.