I can't comment on the Momentum and Polestar. Ask your dealer if it can be installed.
In terms of Polestar on top of the RDesign 248 hp T5 motor, it's not so much a huge leap from a "doddering" 248 motor to Polestar "hyper-drive". It's more about keeping the motor in lots of torque, including changing transmission shift points. Throttle response is "like it happened yesterday". Think of Polestar as an enhancement, not a new motor. I included it in my purchase and did some negotiation in the process. List price is $1300.
Again, ask your dealer if Polestar firmware can be loaded Momentum.
See my latest post about thrashing the RDesign - Polestar definitely added to the fun.
It’s all about the way you going to drive your XC40. If you have a volvo it’s to be safe. this is not a performance brands. But if you do want performance make sure have Polestar.
Only some people know about polestar (previews Volvo customer) , now, the good thing for additional $$$ you can add it to you vehicle. Ask to the dealer.
Price msrp $1250 around. Volvo May send you a coupon 20% Off accessories and part. It will be nice to us it.
I hope this help you.