And that's where you're wrong. The alpha strike is the exact same as other 19 point AP guns, the Chally is not special in this regard and not "high-penetrating". Max. Damage per hit aka alpha strike is a component of dps, the other is rate of fire. Effective dps is both of these against a given targets armor and with a given guns accuracy (chance to hit per shell). That you have to input target armor to get a useful dps reading goes without saying, really.

There's a bunch more cons but i'm sure you'd insist on these being situational and subjective too so no point in arguing.

I'm aware there is situations in which 1st armoured can shine and it's possible to make them work. The question is just why bother unless you're larping the british? Other nato divisions offer more consistency across all situations and some even surpass 1st in the ones where it's remotely useful. There is no reason to play 1st and that's why barely anyone does.