I've been thinking about this very same issue, also for 90% pavement use. I've dug through hundreds of reviews on all sorts of vehicles and the general trend I've seen is that the 5100's aren't as nice on pavement as OEM, and the 6112/5160's are maybe nicer on pavement than OEM (as well as being Vastly better off-pavement). This is just based on subjective reviews from random internet weidos, so who Really knows if it's actually better or they're stuck in the confirmation bias circle (meaning they know they spent $1000 on suspension, so they make themselves believe it's actually better ~ happens behind the scenes.) Knowing a little bit about how suspension works because I did it for a job (lol, 20 years ago ~ but hey, I'm certified by Penske to work on their shocks), I can see how the 6112/5160's could perform better than OEM and be noticeable in on-road conditions... at least in theory.

I think I'm going with the 6112/5160 set for a few reasons. 6112's because they are a designed system, no "works within this range" funny business. I've done enough 'one size fits all' work to know that's complete bunk and should Really be labeled 'one size fits nearly no-one'. The 5160's because they're matched to the 6112's. I have the money to spend, though just barely, and have long since learned that when you can afford to buy a better product, you get both better results but better resale.

I'm not looking for a "lift", which might be one reason to go with the 5100's (for the Tundra IIRC? Which are longer). Extreme budget restrictions would be another reason, not only are the 5100 units cheaper but you could re-use the springs (or take your chances with cheap used springs, or cheap non-OEM springs).

If you haven't done all the Other preventative maintenance to your truck, like lower ball joints, radiator, etc... and buying the 6112/5160 set means that would have to wait or not be done at all, then go with the 5100's and put the money towards the other truck stuff.