This whole obsession with 'minimum change' is going to cost Boeing down the road.
The Airbus design lends itself to a new engine with no compromise on Fan size.
The A320 itself is still reasonably modern and with these new engines should be, and is a good seller.
It is an interim aircraft but not to the extent of the 'max'
Boeing has made a big mistake here in continuing to 'warm up' the ancient 737.
'Interim Aircraft' have a habit of staying around a lot longer than you might think and while the AB product will keep selling well I think Boeing have shot them selves in the foot by catering mostly to SW.
Perhaps the technology is not there yet for a mini 787 but, at a minimum they should have completely upgraded the cockpit and lengthened the main landing gear to allow for the biggest fan that makes sense.