I have both types of W108's,
Their metallurgy is superior to all others
Engines are both mechanically robust depending upon maintenance, oil changes, the valves will got to 150K blocks to 200-300k+, (I pulled the heads off a 4.5 at 239K and cylinders were perfect, after valve job smogged less than a newer car.) of course the FI system is more adjustable than the newer cars, Analog Vs Digital.
If you factor the total cost of ownership (acquisition and maintenance) over many years, these are the cheapest cars on the road today.
One friend calculated under $25/month over 8 years, included a trans rebuild, shocks, tires, excepting fuel. etc...
It is W108 4.5 which the original owner swapped for a newer $45k volvo, the guy almost cried when we left his home, I know he regreted listening to his kids who told their dad to get rid of that "old" car.

New is not better and will cost you more.
Parts not payments