Speed is also very important. It gets you into good positions early and also allows you to get side shots/flanks where the somewhat lower HEAT pen matters less. I personally have never had trouble with the 310 HEAT pen of the 1b, skoda t50, or the kpz 50t. Very few situations that I had where I wished I had the AE's higher HEAT pen. The 310 HEAT pen still works (although less % chance) against stuff like Maus turret, E100 turret, or Jap heavies. The overall package of the 1B is massively better than the AE, but to get use out of higher mobility tanks requires better skill. AE much more noob friendly. -20 mm of HEAT pen for an overall better package is worth it IMO, also 1b basically has no cupola (hull is worse than AE though).

So I disagree on your statement that gold pen is what matters at higher tiers. If gold pen was the most trustworthy metric for the effectiveness of a tank, then how come tanks like the VZ. 55 are doing well despite bad gold? This is not me trying to say that high gold pen is useless, it has its place and if I could, I'd definitely like 330 HEAT on the 1b. But 1b has to have some tradeoffs for it being basically better than AE in every other aspect.

AE still good tonk though.