Hi Paul, the 2023 model had some changes, being a change of manufacturer of the brake components used and I believe traction control came in as well, the dash was changed to a metal painted finish and airbags fitted, plus I think near this year the sound system was changed. So yes, they have the latest bells and whistles. The earlier cars had a veneer wood dash similar to the traditional design and brakes that are fine when well bled. I was told the later brake system has a better "feel". Dont think much else has changed apart from around the MY2021 year the top design was changed, the earlier Plus Six cars have "flaps" over their upper doors when its up, the later model seals against the top itself, so its a little faster to get in and out. Also from around mid 2020 the lower seat section design was changed and this sat the driver lower and gave more leg side support. Most folk liked this, but I prefer the earlier design.. Must be the shape of my rear end..

I own a mid 2020 model, so I dont necessary look at the latest "improvements" as improvements, just design changes, some introduced from customer views, some from supplier. The pre 2023 cars may have a more raw feeling to you when driven and from my perspective that is what I wanted. I absolutely hate the later Plus Six dash design, be it that it now has airbags. Also of note the later cars with airbags can not have their steering wheel changed to the older Moto-Lita design, you have to use the MMC version.
I think you should road test all the years, they will feel a little different and then make a call. The Plus Six is a great car, an early "sorted" car is in my view as good as the latest version..