The 3BM-42 projectile is generally similar to the 3BM-32 in external layout due to the use of a similar "bucket" type sabot, but it has a more complex construction using jacketed tungsten penetrators instead of a depleted uranium rod, and most importantly the projectile is significantly lengthier. Penetrator L/D ratio for 3BM-42 is 20:1 compared to only 13:1 on 3BM-32 (you will note Fofanov doesn't list it because it was not known when he made his estimate). Also, there are no reliable formulas for estimating the penetration characteristics of depleted uranium rounds, as we don't yet have accurate data points for them. All calculations for the penetration values of DU rounds I have seen until now are derived from Odermatt formula originally made for tungsten and steel perpetrators and simply modified by using a value multiplier (sometimes called "material modifier") which is no more than estimated constant. Therefore estimates tend to vary a lot.
The weakness of jacketed long rod penetrators is its reduced penetration power against homogeneous steel armour compared to a monobloc penetrator. However, it was hardly an issue as homogeneous steel armour was not used in tanks produced after the 1960s, and it never exceeded levels of 250-300mm RHAe which was not an issue for any modern APFSDS. By the mid-1980s the generation of NATO main battle tanks were using spaced NERA armour against which 3BM-42 was superior.
Penetration into spaced targets (3BM-32):
7-layer array at an angle of 60 degrees (630mm LOS) could be defeated at 3200 m.
7-layer array at an angle of 30 degrees (620mm LOS) could be defeated 3200 m.
3-layer spaced array at an angle of 65 degrees (1830mm LOS) could be defeated at 5000 m.
Penetration into spaced targets (3BM-42):
7-layer array at an angle of 60 degrees (630mm LOS) could be defeated at 3300 m.
7-layer array at an angle of 30 degrees (620mm LOS) could be defeated 3800 m.
3-layer spaced array at an angle of 65 degrees (1830mm LOS) could be defeated at 2700 m.
Mikhail Rastopshin give 250mm RHA at 60° for BM-32 at 2km and 210mm at 60° for BM-42 (230mm at 60° according to "Textbook of Means of Defeat and Ammunition" (Учебник Средства Поражения И Боеприпасы) published by Bauman Moscow State Technical University).
However, 3BM-32 is only rated as 400mm at 2km at 0° according to Mikhail Rastopshin (430mm RHA at 0° on advertising plaque), while 3BM-42 is listed as 520mm at 0° at 2km in the above mentioned textbook.
Hence 3BM-32 only holds a slight advantage over 3BM-42 on sloped homogeneous steel targets, which is irrelevant in game terms as 3BM-32 is already overmatching such targets by a far margin, while 3BM-42 is better against composite multilayer target arrays like those seen on Leopard 2 or M1 Abrams.
In principle, using RHAe as a measure to compare modern APFSDS penetration and armor protection is not a good method. The interaction between each armor type and penetrator type are unique, therefore trying to shoehorn the provided protection into one single value versus all different types of APFSDS ammo can be quite misleading. APFSDS ammunition isn't even tested against RHA anymore unless a customer demands it. However, for us gamers, it still remains the best solution we have at the moment.