wow the 140 is seriously not nearly as good as the T-62A and I don't think it ever was. I never really played this tank for any big amount of time. I got the T-62A first and got the 140 for completion's sake and only really took it out every now and then for the lulz. Now not having a T-62A that's ready to go, I can articulate as to why I somehow felt better in the 62.
The speed difference is negligible. Seriously I don't notice it at all, but that's not a big deal.
Frontal armor is better. 140 is better in the situation where you must scrape sides and, with practice, it actually is able to corner better than any medium.
Turret armor I never really saw as an issue and still don't. Both had pennable hatches before in a close up situation, and both could be penned by the right gun. They're a little more balanced now so this is not that big of a deal.
It's the gun and the turret speed that make this way worse though. What's the point in being able to go faster if you can't fire at multiple targets or change aiming direction? It is the most noticeable downside to the 140. That and I do notice I miss more often than I would in a 62, which I think is because of the aim time.