So, I’ve had a number of OHV 4.0 and they’re not a bad engine at all. I’ve also blown up a few. They are easy to work on and pretty simple. The SOHC has a little more pep (mom’s Explorer has one that’s somewhere around 180k+), but timing chain issues have always been in the back of the mind on that one.
The 4.0 OHV was essentially a bored and stroked 2.9, so to some degree it‘s an aged design with some inherent weak spots.
I really don’t have much of a preference other than my newest vehicle so far is a 2000, which means I’m OHV all around. The good thing for me is that the basic engine for the OHV is the same from introduction (1990, IIRC) to 2000 is the same. My 89 Choptop has a 96 Explorer 4.0 in it, I just had to change the wiring harness and fuel rail up to make it happy. My 92 Ranger has a 2000 Ranger 4.0, same deal. Simple.
If you really want power, you need to get away from the 4.0 engine. They make reasonable power and things like supercharger/turbo and such can provide a nice boost, but they were never built as performance motors, either design.
The auto transmissions however, are the bane of existence for either 4.0 in stock form. Really any RBV from the introduction of the infamous A4LD on up. Better cooling, shift kit and valve body work and the like opens up a whole new world there. My 92 Ranger would light up both back tires from a stop just by hitting the gas too hard after that. Empty or lightly loaded, anything beyond half throttle wanted to light them up from a stop. Even the newer 4R and 5R transmissions can benefit from this sort of thing along with the 4R70 that was behind the 5.0