These distances are not great, but the Northern terrain of the Rhinogs is as brutal as it comes, and you need to search hard in the Scottish Highlands to find terrain as unforgiving as the Northern Rhinogs.
Starting from Bronaber on the A470 Trawsfynydd road, which ever route you decide on, you will be approaching the Rhinogs from their most rugged side.
Theres the Bwlch Drws Ardudwy route that will eventually bring you to Harlech, or still the savage Rhinog Fawr route leading towards Yr Lether.
There is no real easy route from the A470 side of the Rhinogs, but i recon the Barmouth route is the easiest, as once your past Rhinog Fawr, over Yr Lether, its very easy going from then on.
The Harlech direction from the Trawsfynydd side is a serious adventure, by far the toughest 13.4miles you will find outside of Scotland.
I attempted the Northern Rhinogs from Bronaber several months ago, an easy start, but one hell of a brutal assault on the limbs, and for such a short distance it will take several long hours if the weather is favourable.
I would much prefer a traverse of the Rhinogs from the Talybont side, starting with Moelfre, and then on towards Yr Lether, and if you really feel adventurous on to Rhinog Fawr.
Moelfre- Yr Lether- Diffwys- and on via Bwlch yr Rhiwgyr to Barmouth.
A far easier Rhinog experience, far easier on the limbs, all over stunning desolate country, with probably not a single person along your way.