For variety of riding, the Blackmill Rat-run enduro was a better mix and probably harder too.
Have you done the Dyfi before? as to compare the two is like comparing a 3K fun run with a mountain marathon. The Dyfi is much much easier than the Rat run in terms of distance and the difficulty of the tracks.
There was a thread on mtb-wales about them re-running the Rat Run,and I have no doubt that is would be easily the toughest Enduro in the UK, as it had something like 8,000ft of climbing in the 65K route made more difficult by it being held in April so everything was nice and tacky.
Not sure how successful it would be as people don’t like to be shown to be average fitness and ability as the course was **** brutal