at the risk of perhaps stating the obvious, and preaching to the choir...
car mfrs are going from V8's to V6's, and from V6's to to turbo-4's, because of the Corporate Average Fuel Economy (CAFE) regulation being imposed on them by the climate extremists and tree huggers. The car still weighs the same, so they need to boost the output of the tiny little four-banger so it'll go up a hill, and they do that with the turbo. The point being that in general, the four-banger will lead a more highly-stressed life in order to move those 3,000 lbs of weight up and over Red Hill freeway. So IMHO, those little 1.6L or 2.0L engines, that are being boosted to try to match the output of previous 3.0L, 4.0L engines will wear out sooner, ALL THINGS BEING EQUAL.
Highly stressed means more bearing loads on the crank, the rods, pistons. Higher heat loads, operating temps internal to the engine that have to be dissipated. Sometimes they spin the engine to higher RPMs in order to get the power to get up Red Hill, whereas before, they'd let the engine displacement, cubic inches do the work with torque. This also shortens engine life.
so how do you make up for that? have to change the oil more often, so that the bearings last longer, piston rings, piston walls last longer. Oil breaks down sooner due to exposure to higher temps and combustion products exposure. This creates a more frequent and greater maintenance burden that is incumbent upon the owner. Hopefully the cooling system is right-sized, but the rubber hoses will not last as long due to them working harder to dump the heat out of the engine. Plastic stuff being exposed to more heat will become brittle and crack sooner.
I'm sure many of us have experienced the frustration of working on older vehicles and some older plastic part just snaps off or breaks in two, just due to age, heat exposure, and then you find out it's discontinued, no longer available, and then it's "improvise or adapt", or eBay for used parts. Well, maybe not all of us.
In general terms again, a bigger turbo-V6 will lead a less stressful life than a smaller-displacement turbo-4 since it's likely not being worked as hard to get the same power output.
If the vehicle you want is only available with a turbo-4, then you got no choice. If you're looking for that 10-year, 20-year, 30-year longevity, then get the bigger engine, avoid the turbo, if possible, and change your oil when you're supposed to.
JMHO, YMMV.