The improvement in armor is only noticeable specifically on the mantlet. The hull front still isn’t enough to stop something of the likes of the US 76 mm, and the turret cheeks near the mantlet are a still a weakspot on the turret.
The 90 mm is powerful, but the stabilizer and mobility of the T20 more than make up for it. On a straight line, in a good road, it takes the longer for the T25 to reach 45 km/h (26 seconds) than the T20 to reach its top speed of 56 km/h (25 seconds). It takes 11 seconds for the T20 to reach 40 km/h, and 21 seconds for the T25 to do the same.´
The hp/ton goes from 17.78 to 13.70. It takes 9 seconds for the M36 to reach 40 km/h compared to 14 seconds on the M36B2.
M82 is still the main round and the high acceleration allows the M36 to not switch rounds as often. HEAT-FS is only really useful in frontal engagements which is the kind of engagement that should be avoided in the first place with an M36. The roof can only protect against either rifle caliber AP rounds or smaller HE rounds, and that’s assuming that the rounds don’t hit on the big hole that exists on the roof. More powerful AP rounds just go through, and more powerful HE rounds bypass the armor via overpressure, which the M36B2 is still vulnerable to.
Without ready rack the reload rate of the Fireflies receives a 1.5× multiplier, making it 8.82 seconds with a fully maxed out loader. The Sherman VC with track armor is also the Sherman with the worst hp/ton in the entire game so it’s more than “moderately decreased mobility”. Even with track armor, the armor is nothing phenomenal as all the Fireflies have early Sherman hulls with the vulnerable driver and assistant driver bulges, except the Tipo IC which has the well known cast front. Stuff like the KV-1 L-11 and M4 don’t have much trouble against Fireflies, even though they face these tanks in full uptiers.
Beyond all that, penetration only matters if there actuall exists targets against which it matters, which isn’t really the case if you compare the 17 pounder to something like the US 76 mm at this BR, unless the 17 pounder has APDS. The M4A1 (76) sits at 5.0, and is a better vehicle than the 4.7 Fireflies.
The basic APCBC is slightly more powerful than the US 76 mm in penetration, but has no explosive filler, and its APDS was massively nerfed with the update to APDS rounds. All of that and the Comet also has a reload rate identical to that of the Panther.
As I said for the Fireflies, penetration only matters if there are targets against which it can be used.
You still can’t penetrate a Panther with PCOT-51P, even at 30 meters. You can penetrate a Jumbo upper plate if it is unangled up to about 400 meters, but that is it. And you still have the early Sherman hull with and added weight.
I do not know a single person that has bounced on it, including myself. It is a massive target flat target, and on top of that it is cast armor meaning it is 103.4 mm RHA equivalent, and you cannot angle at all as the turret side is 30 mm. For the reload you specifically picked russian cannons which generally have longer reloads for their power. You have the Nashorn at 5.3 with the long 88 which, although has less pen, has much more post pen and has a 6.67 second reload.