First of all, it should be 87W where I mention 85W since I mean USB-C chargers, and for 15"+
I checked Apple's Store. What I found 87W adapter is no longer available there.
If I check some other store, 87W is with 4-months Apple Music, and ... sold out.
So if would look for another USB-C adapter for 15" MBP, you have only 96W option.
As for you guess replace vs new. It should be rather one more adapter for fields trips.
In office I have a monitor with PD.
Original one will be always on my home desk.
And new one is to be in a backpack.
@nicho , you are right, there is no benefit. And there is no choice.
BTW new one should be heavier, a bit, but heavier anyway