It still does more damage and is far, far more mobile. While also having more penetration for ~reasons~ now.
The extra 40 damage is only relevant vs medium armor if there are other sources of AT on the field to help round down the number of shots needed to kill a P4. The extra 40 damage is a lot more important vs heavy tanks because it allows the Jackson to KO a heavy in the same number of penetrations as before. You could say the Jackson traded the raw DPS of a SU-85 for better penetration vs heavies.
It remains to be seen if the Jackson performs too well against heavies.