OEM Dunlops are fine, and I strongly recommend them for one good reason, all the milles testing by HD on a variety of miles over all models over many different conditions have yielded THEIR selection, most of us do not have the resources or the laboratory testing results or time to verify their results, but rider opinons so far seem indicate most people feel MOCO made the right choice and contracted the best deal with Dunlop for so many years running (since the 60's I think).
True, metric bikes commonly used Bridgestones OEM graded "sub-premium tires" up until recently, due to their intense buying power to leverage great deals, and even special low cost Dunlops to sell new, strictly due to the fact the performance crowd was not really interested in OEM tires and pitch them at 1st opportunity anyway (they wanted the stickiest best handling rubber, mileage being only a secondary concern). Only the big touring bikes got harder, long mileage rubber, but again even touring riders were picking Michelin, Avons and others because they wanted radials w/ softer compounds for ride and comfort as well as mileage.
I've been running Metzler radials on my sportbikes for years and like them the best, but this is my first experience with the Metzler bias ply tires on my Sporty (because I like Metzler experiences so far, and so is still a work in progress), they handle just fine, slightly larger footprint and ride height then equivalent sized Dunlop, but as far as mileage "-- the jury is still out." Selection comes down to a matter of personal taste and experience...JMHO!