I’ve tried a 1-1/8″ and a 1.5″ Revelation fork on Ragley Mmmbop frames – both forks were the Team version with 20mm bolt through.
The 1-1/8″ was very flexy and I sold it on to run a Fox 36 1.5″ fork. I then picked up the 1.5″ Rev as I hoped it would be less of a noodle than the 1-1/8″ version… which it kind of was. The 1.5″ steerer definetly reduced the fore/aft flex of the Rev but I still found myself sawing at the handlebars as the legs of the fork twisted.
Summary – In my experience 1.5″(and hence tapered ) steerers are definetly stiffer in front to back flex than 1-1/8″; but they are not enough in themselves to make much of a difference unless the whole package is suitably stiff.
Depends how you ride and if you can live with flex for reduced weight, or want a carbon steerer which is lighter etc etc, but I can see a benefit to the standard… although I liked the 1.5″ steerer and still have forks with it 🙄