I suspect the best reason for upgrading is access to 24GB of RAM and maybe the hardware video encoders if that's your thing. Otherwise, M2 is a very solid iteration, but probably not worth dropping that much money if you already own an M1 system.
I couldn't find any info on this, is this the same Magsafe as the 2015 devices, i.e. can I use existing old chargers? If so then I might even consider upgrading just due to this (I also have a 12/24V Magsafe charger).
24 GB RAM would be nice compared to 16 GB currently, but it's not something I'd really need.